Ionic liquids (ILs) have been receiving increasing attention as a potential decarbonization solvent. However, the enormous number of potential ILs that can be synthesized makes it a challenging task to search for the best IL for CO2 removal from methane. In this work, a method was proposed to screen suitable ILs based on the COSMO-RS (conductor-like screening model for real solvents) model, an absorption mechanism, and experimental data. Besides the Henry’s constant, the viscosity and toxicity of ILs should also be taken into consideration for an industrial decarbonization process. Furthermore, process simulation was performed to evaluate the new IL-based decarbonization technology. Considering CO2 solubility, CO2/CH4 selectivity and toxicity and viscosity of ILs, [bmim][NTf2] has been screened to be the potential solvent among 90 classes of ILs. Based on reliable experimental data, a rigorous thermodynamic model was established. The simulation results have been found to agree well with the available experimental results. Two process flow sheet options, use of two single-stage flash operations or a multistage flash operation following the absorber, have been simulated and assessed. Compared with the well-known MDEA (methyldiethanolamine) process for CO2 capture, the single-stage and multistage process alternatives would reduce the total energy consumption by 42.8% and 66.04%, respectively.

Ionic liquids (ILs) offer a wide range of promising applications because of their much enhanced properties. However, further development of such materials depends on the fundamental understanding of their hierarchical structures and behaviors, which requires multiscale strategies to provide coupling among various length scales. In this review, we first introduce the structures and properties of these typical ILs. Then, we introduce the multiscale modeling methods that have been applied to the ILs, covering from molecular scale (QM/MM), to mesoscale (CG, DPD), to macroscale (CFD for unit scale and thermodynamics COSMO-RS model and environmental assessment GD method for process scale). In the following section, we discuss in some detail their applications to the four scales of ILs, including molecular scale structures, mesoscale aggregates and dynamics, and unit scale reactor design and process design and optimization of typical IL applications. Finally, we address the concluding remarks of multiscale strategies in the understanding and predictive capabilities of ILs. The present review aims to summarize the recent advances in the fundamental and application understanding of ILs.

The inherent structure tunability, good affinity with CO2, and nonvolatility of ionic liquids (ILs) drive their exploration and exploitation in CO2 separation field, and has attracted remarkable interest from both industries and academia. The aim of this Review is to give a detailed overview on the recent advances on IL-based materials, including pure ILs, IL-based solvents, and IL-based membranes for CO2 capture and separation from the viewpoint of molecule to engineering. The effects of anions, cations and functional groups on CO2 solubility and selectivity of ILs, as well as the studies on degradability of ILs are reviewed, and the recent developments on functionalized ILs, IL-based solvents, and IL-based membranes are also discussed. CO2 separation mechanism with IL-based solvents and IL-based membranes are explained by combining molecular simulation and experimental characterization. Taking into consideration of the applications and industrialization, the recent achievements and developments on the transport properties of IL fluids and the process design of IL-based processes are highlighted. Finally, the future research challenges and perspectives of the commercialization of CO2 capture and separation with IL-based materials are posed.

A series of adamantane-based ionic liquids (ADM-ILs) with [MFn]− anions were synthesized as cocatalysts for the alkylation of isobutane and butene. By systematically tuning the structures of the cation and anion and their combination, we obtained the optimized ionic liquid, ADM-C12-SbF6, which exhibited significant enhancements in the C8 selectivities [especially to trimethylpentanes (TMPs)], the research octane number (RON) of the alkylate products, and the lifetime of sulfuric acid. The selectivity to TMPs was improved from 81.9% to 84.5%, and the alkylate RON was improved from 96.6 to 98.6 upon the addition of the ADM-ILs. In addition, the lifetimes of the ADM-IL/H2SO4 systems were increased to twice that of H2SO4 alone. Based on experimental measurements and DFT calculations, all of these enhancements were attributed to the multifunctions cooperatively integrated into the task-specific ADM-ILs, such as surfactant action, improving the interfacial properties of the acid/hydrocarbon biphases; buffer action, stabilizing the acidity changes during the reaction process; and hydride donor action, increasing the H– transfer rate, which promoted the production of TMPs. This study is beneficial for improving the isobutane alkylation process catalyzed by concentrated sulfuric acid.

A simple in situ self-assembly selective synthetic strategy for one-step controllable formation of various three-dimensional (3D) hierarchical Co3O4 micro/nanomaterials with peculiar morphologies, uniform size, and high quality is successfully developed. The morphological control and related impact factors are investigated and clarified in detail. The results further clarify the corresponding mechanisms on the reaction process, product generation, and calcining process as well as the formation of specific morphologies. Furthermore, the superior catalytic properties of these materials are confirmed by two typical Co-based energy applications on the decomposition of an important solid rocket propellant, ammonium perchlorate (AP), and dye-sensitized solar cells (DSSCs). The addition of Co3O4 materials to AP obviously decreases the decomposition temperatures by about 118–140 °C and increases the exothermic heat to a great extent. As the substituted counter electrodes of DSSCs, the 3D hierarchical Co3O4 materials exhibit attractive photovoltaic performances. These findings provide a facile and effective way for designing new types of 3D hierarchical materials toward high catalytic activity for energy devices.Keywords: 3D hierarchical Co3O4 micro/nanomaterials; ammonium perchlorate; dye-sensitized solar cells; in situ; superior catalytic properties;

A fluidized bed process for the one-step synthesis of methyl acrylate (MA) using methyl acetate (Ma) and formaldehyde (FA) was developed for the first time. New spherical antiwear acid–base catalysts Cs–P/γ-Al2O3 were prepared using ultrasonic impregnation method and characterized with XRD, BET, SEM, PSD, ICP, TG/DTA, NH3-TPD, and CO2-TPD methods. Catalytic performance was evaluated, and 10.0 wt % Cs–5.0 wt % P/γ-Al2O3 with weak acid–base sites was determined to be the best catalyst for MA production. Response surface methodology (RSM) was employed to optimize aldol condensation of Ma with FA over 10.0 wt % Cs–5.0 wt % P/γ-Al2O3. The effects of various process parameters such as reaction temperature, molar ratio of Ma and FA, and liquid hourly space velocity (LHSV) on MA yield were addressed by Box–Behnken experimental design (BBD). The coefficient of determination (R2) of this model was 0.997, and 39.5 mol % yield of MA was obtained after optimization. The developed catalyst exhibited high stability, with no significant decrease in catalytic activity after 1000 h of lifetime evaluation.

The high viscosity of ionic liquids (ILs) is one of the impediments to their application in industry. Understanding the relationship between structure and viscosity is a key issue for the directed design of ILs with low viscosity. In this work, the microstructures and interactions of three representative imidazolium-based ILs were studied by quantum chemistry calculations and molecular dynamics simulations to investigate the origin of different viscosities. An all-atom force field for difluorophosphate ([PO2F2]) anion was developed. The sandwich structures of hydrogen-bond networks were observed. A relationship between the number and energy of hydrogen bonds and the viscosity was proposed. The order of interaction energies is consistent with the trend of experimental viscosities. The simulation studies suggest that the hydrogen bonds and interaction energy play important roles in determining the viscosity of an IL.

Carboxylic acid-based ionic liquids (CAILs) were designed and synthesized. They displayed temperature-dependent dissolution–precipitation transitions in propylene carbonate (PC) by controlling the chain length of the carboxyl group. It was found that it could be attributed to the temperature-controlled hydrogen-bond formation/broken between the CAILs components and PC by NMR investigations and DFT calculations. Such a unique phase behavior was successfully utilized for the cycloaddition reaction of CO2 with epoxides. Due to the activation of epoxide assisted by the hydrogen bond, the optimal ILs could show a 92% yield of PC within 20 min and quickly precipitate out from a homogeneous system at room temperature for easy recycling. The reversible phase transition phenomenon supplied an efficient way to combine activity and recovery of homogeneous catalysts, which is a benefit for energy-saving and industrial applications.Keywords: CO2 conversion; Cyclic carbonates; Ionic liquids; Reaction−separation; Temperature-controlled;

Ionic liquids (ILs) have been employed as solvents for dissolving wool keratin which can be further regenerated and applied in high-value and biocompatible keratin-based materials. It is urgent to determine the changes in disulfide bonds and keratin microstructures in the dissolution process for designing efficient ILs. Herein, the breakage of disulfide bonds by ILs was verified for the first time using a model compound, oxidized glutathione. Furthermore, at least 65% of disulfide bonds in keratin should be cleaved in order to be dissolved in ILs. The keratin regenerated in a series of ILs, and variable conditions were also characterized by a combination of S-linked techniques. The results indicated that changing both anions and cations can lead to a dramatically different ability to cleave disulfide bonds, while the side chains of the cations have little effect on it. Also, the dissolution variables, such as temperature and time, led to different amounts of disulfide bonds remaining in the regenerated keratin. Finally, molecular dynamics (MD) simulation found that the distribution of ILs around cystine was linked with the ILs’ disulfide bond cleaving ability.Keywords: Cleavage; Disulfide bond network; Ionic liquids; Wool keratin;

Single-component anode materials can barely satisfy the growing demand for next-generation Li-ion batteries with higher capacity and cyclability. Thus developing multi-component synergistic electrodes has become a critical issue. Herein, inspired by natural corn, a ternary hierarchical self-supported array design is proposed. Based on a sequential transformation route, Si/C-modified Co3O4 nanowire arrays are constructed on 3D Ni foams to form a binder-free integrated electrode. Specifically, an ionic liquid-assisted electrodeposition strategy is employed to prepare discrete ultrafine Si nanoparticles on nanoscale array substrates, which follow the Volmer–Weber island growth mode. In this corn-mimetic system, kernel-like Si nanoparticles and a husk-like carbon coating layer function as enhancing and protecting units, respectively, to improve the capacity and stability of the cobalt oxide basic unit. Taking advantage of a synergistic effect, the ternary nanoarray anode achieves a significant performance enhancement compared to pristine Co3O4, showing a special capacity as high as ~1,000 mAh·g−1 at 100 mA·g−1. By extending this corn-mimetic hierarchical array design to other basic, enhancing, and protecting units, new ideas for constructing synergistic nano-architectures for energy conversion and storage field are developed.

Lithium–sulfur suspension flow batteries are a promising technology for large-scale energy storage, but long-term stability of the suspension catholyte is urgently needed for future application of this system. Here a special self-stabilized suspension catholyte is designed and prepared based on a pie-structured sulfur-Ketjenblack@reduced graphene oxide (S-KB@rGO) composite. In the S-KB@rGO suspension, the sulfur nanoparticles are loaded onto the conductive KB by an in situ redox reaction; the special hyperbranched structure of KB enhances the stability of the suspension; rGO sheets which wrap the S-KB particles not only act as a multilayered physical barrier for sulfur immobilization, but also facilitate electron transportation in the whole suspension. Therefore, a suspension catholyte with long-term physical and electrochemical stability is achieved by the synergetic effect of the KB and rGO. Li–S flow cells with this catholyte show excellent cycle stability (more than 1000 cycles with 99% coulombic efficiency) and low self-discharge (1.1% loss per day). Continuous charge/discharge tests in different flow modes are performed and the influence of the flow rate on the flow battery performance is discussed. The smooth operation in long-lasting flow mode further demonstrates the stability of the suspension catholyte.

Phosphonium-based polymeric ionic liquids (PILs) have been prepared in a controlled way by using a microfluidic technique within an improved membrane microdevice. Using this method, the average diameter sizes of the particles could be tuned from 6.4 to 375 nm through varying the dispersed phase flow rates from 1.0 to 7.0 mL min−1. The nanoparticles were characterized by FTIR, SEM, HRTEM, EDS, TGA and ICP, and their catalytic properties were estimated in the cycloaddition of CO2 with epoxides. It was found they could deliver good to excellent yields with selectivities of more than 99%. 1-Bromoacrylic acid-decorated nanoparticles (NPILs-BPA) were especially effective. Additionally, the activity displayed obvious size-dependence, increasing for the smaller particles, and the particles were stable when recycled seven times, retaining their catalytic activity and selectivity. Meanwhile, the ability of NPILs-BPA to provide carboxylic acid groups and act as a hydrogen bonding donor to activate the ring-opening of epoxides was tested by in situ FTIR. This work provides a continuous, simple method for the preparation of PILs with controlled nanosizes, and offers the potential for scale-up and throughput in industrial applications.

A highly efficient synthesis of isosorbide from sorbitol was developed using Brønsted acidic ionic liquids (BILs) as the catalyst for the first time. The structure–performance relationship was discussed extensively and a proper value of the Gutmann acceptor number (AN) rather than the inherent of acidity was found to be essential for an optimized yield of isosorbide. In addition, the excellent behavior of preferred BIL-4 in the consecutive recycling tests renders the construction of a continuous process probable. Systematic optimization demonstrated that a yield of 82% of isosorbide with a purity of 99.3% could be reached at balance.

Density functional theory (DFT), atoms in molecules (AIM) theory, natural bond orbital (NBO) analysis, and reduced density gradient (RDG) analysis were employed to investigate the mechanism of lignin dissolution in imidazolium-based ionic liquids (ILs). Lignin was modeled with guaiacyl glycerol-β-guaiacyl ether (GG), which is one type of β-O-4 linked dimers. Hydrogen bonds (H-bonds) are studied specifically and characterized by different methods to evaluate the strength of interaction between ILs and the lignin model compound. From the theoretical results, it is observed that H-bonds between anions and the GG model are stronger than those between cations and the GG model. Also, anions have the strongest interaction at the α-OH position of GG, while cations have the strongest interaction at the γ-OH position of GG. In addition, anions Cl, OAc and MeSO4 have much stronger H-bonding ability than PF6, and the length of the alkyl chain does not have a significant influence on the cation–GG interaction. This work also simulates the interaction between the GG model and ion pairs, with the results suggesting that anions in ion pairs play a key role in forming H-bonds, and cations have a π-stacking interaction with GG. The calculation data provide the interaction mechanism of lignin dissolution in ILs to some extent.

Cost-efficient and environmentally benign treatment of NH3-containing exhaust gas has been a challenge. Ionic liquids (ILs) due to their unique structures and properties are recognized as potential solvents to absorb NH3. In this study, three types of ILs, including [Bmim][NTf2], [Bim][NTf2], [HOOC(CH2)3mim][NTf2], were designed and synthesized with various hydrogen bond donating abilities and characterized based on their thermodynamic dissociation constants (pKa). The results showed that protic ionic liquid (PIL) [Bim][NTf2] with a moderate pKa value had the highest NH3 absorption capacity (up to 2.69 mol NH3 per mol IL, 313 K, 100 kPa). Experimental characterization and theoretical calculations verified that such extremely high NH3 absorption capacity for [Bim][NTf2] resulted from the interactions between H-3 on the imidazole ring and the NH3 molecule and NH3 molecules sintering themselves. Furthermore, stable absorption performance was recorded for [Bim][NTf2] over four cycles, implying potential applications in the industry for NH3 recycling.

A protocol for the cobalt-catalyzed oxidative esterification of allylic/benzylic C(sp3)–H bonds with carboxylic acids was developed in this work. Mechanistic studies revealed that C(sp3)–H bond activation in the hydrocarbon was the turnover-limiting step and the in-situ formed [Co(III)]Ot-Bu did not engage in hydrogen atom abstraction (HAA) of a C–H bond. This protocol was successfully incorporated into a synthetic pathway to β-damascenone that avoided the use of NBS.Download high-res image (120KB)Download full-size image

•Methacrylic acid was extracted from diluted aqueous solution by ionic liquids.•Ionic liquids have shown better extract ability than hexane.•Hydrogen bonding interaction was confirmed by IR and quantum chemical calculations.•[N8881]Cl has strong hydrogen bond basicity value of 1.499.•Partition coefficient of methacrylic acid is achieved 42.15 for [N8881]Cl.The recovery of carboxylic acids from dilute aqueous solution is necessary but difficult in chemical industry. Methacrylic acid (MAA) is an important chemical widely used in polymer industry. In this work, the recovery of carboxylic acid from diluted aqueous solution by liquid-liquid extraction using ionic liquids (ILs) as extractants was studied. MAA was employed as model carboxylic acid. The partition coefficients of MAA in biphasic system and the extraction efficiencies of MAA were determined for imidazolium-based ILs and quaternary ammonium salt ILs with different structure of cation and anion. The extraction conditions such as extraction time, extraction temperature, mass ratio of ILs to MAA aqueous solution, initial concentrations of MAA, and water content were evaluated. An internal mechanism of the MAA extract by ILs was revealed by combining solvatochromic study, FT-IR and quantum chemical calculations. The results show that the strong hydrogen bond basicity (β) of ILs results in the high partition coefficient of MAA, which provides guidance to molecular design of ILs for the high efficient extractive separation of MAA from diluted aqueous solution. Based on this, IL with strong hydrogen bond basicity ([N8881]Cl) was used to extract MAA from dilute aqueous solution. Compared with hexane which is conventional solvent used in MAA extractive separation, [N8881]Cl can get 49 times higher of partition coefficient value and the extraction efficiency reach 94.57% for the single-stage extraction.

•A universal real component-based characterization approach was proposed.•The compositions of pure components in complex mixture were estimated.•Established the rigorous reaction kinetic modeling of hydrogenation process.•The chemical hydrogen consumption were predicted effectively.Hydrogenation is an important processing technology for upgrading inferior oil. Kinetic modeling for hydrogenation process continues to be a challenging task because of the complex compounds and reactions involved. Therefore, a systematic carbon-number components-based substitution approach was proposed in this work as representatives of real feedstock (e.g. residual oil, vacuum gas oil, coal tar, etc). The primary advantage of the approach lies in direct availability of chemical character and physical property data. The detailed molecular compositions of components were also determined in the optimization algorithm by correlating the bulk experimental properties of original mixture. On this basis, the detailed kinetic modeling of hydrogenation process based on the real components reaction pathway could be constructed. The approach was verified using a set of 64 pure components to characterize the coal tar feedstock and used to simulate the reaction modeling of coal tar hydrogenation process. Results revealed that the hydrogenation product distribution and the chemical hydrogen consumption were predicted effectively. This work provides a significant guidance for the design and optimization of hydrogenation process.

•High specific capacitive TiO2(B)@C/rGO nanoarchitetures were successfully synthesized.•Complete utilization of Faradic and non-Faradic capacitance of nanohybrids was realized by using formulated electrolyte.•4 V operating potential was actualized with the presence of ionogel polymer separator.Novel TiO2(B)@C/rGO nanoarchitectures are fabricated by combining hydrothermal treatment, ions exchange, and topological phase transformation as well as carbon modification. Asymmetric hybrid Li-ion nanohybrids supercapacitors with high energy and power densities are constructed by combining hybridized anode, which can supply both pseudo capacitance from TiO2(B) and electrochemical double layer capacitance (EDLC) from nanocarbons (graphene nanosheets and amorphous carbon layer), and activated carbon (AC) as EDLC type cathode. The high power density is realized readily via both the modification of nanocarbons, which not only improve the electric conductivity but introduce extra Faradic capacitance, and the employment of high-voltage formulated ionic liquids electrolyte as well as ionogel polymer separator. Such a balanceable and complementary design between electrode and electrolyte allow rapid ion and electron transport in ionic liquid-based electrolyte and hybridized electrodes. The maximum energy and power density of 59.4 W h/kg and 17.3 kW/kg can be readily realized at 40 °C on account of the special characteristic of ionic liquids. These results clearly demonstrate that high performance nanohybrid supercapacitors can be actualized through the subtle combination of nanohybridized electrodes and high voltage formulated ionic-liquid/lithium-salt electrolytes, which make them promising power-type energy storage devices for hybrid electric vehicles.Download high-res image (279KB)Download full-size image

A large number of surplus glycerol from the biodiesel production can be used as renewable feedstock to produce glycerol carbonate. In this paper, a series of guanidine-based ionic liquids were synthesized to catalyze the transesterification of glycerol and dimethyl carbonate. The tunable basicity and the anion–cation cooperative effect were responsible for the obtained results. The [TMG][TFE] showed the best activity (turnover frequency (TOF) of 1754.0 h− 1, glycerol (GL) conversion of 91.8%, glycerol carbonate (GC) selectivity of 95.5%) at 80 °C with 0.1 mol% catalyst for 30 min. The reaction mechanism of the transesterification was also proposed.The synthesis of glycerol carbonate from glycerol was catalyzed by guanidine-based ionic liquids. The [TMG][TFE] showed best activity (TOF of 1754.0 h− 1, GL conversion of 91.8%, GC selectivity of 95.5%) at the optimized condition.Download high-res image (58KB)Download full-size image

•A green process using ILs as solvents and co-catalysts for HMF oxidation was developed.•A novel non-noble metal catalyst was used for HMF oxidation without additional base.•The catalyst was stable and its catalytic activity was remained during the reaction process.Base-free conversion of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) was carried out by a simple and green process based on a novel ionic liquid (IL)-promoted non-noble metal catalytic reaction system. Among various of ILs, 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) was found to be the best IL without addition of base as it has stronger hydrogen bonds formation ability and good thermal stability, as well as free to form definite aggregates. In addition, a series of non-noble metal catalysts containing Ce, Fe, Zr were synthesized and the Ce0.5Fe0.15Zr0.35O2 catalyst was found to have excellent activity due to the existence of active iron and zirconium species and the formation of CeO2-based solid solution, which could create more oxygen vacancies and improve the redox properties of catalyst. Under the optimal reaction condition, almost complete HMF conversion and 44.2% FDCA yield were obtained after 24 h at 160 °C over Ce0.5Fe0.15Zr0.35O2 in [Bmim]Cl. More importantly, the catalyst could be reused without significant decrease of its catalytic activity. This research not only develops a more environmentally friendly catalytic system that promotes the base-free oxidation of HMF into FDCA, but also provides an economic route to produce FDCA.

A new green cellulose extraction method – the selective degradation dissolution extraction (SDDE) method based on the [Bmim]Cl–AS (i.e. amino sulfonic acid (AS)) solvent system – was found which could rapidly extract a high yield and purity of cellulose from cornstalk at relatively low temperatures in a remarkably short time. In the SDDE method, the lignin-carbohydrate complex protective layer (LCCPL), which wraps around the cellulose, was selectively depolymerized into small molecules; as a result, the rapid dissolution of lignocellulose biomass and the efficient removal of lignin and hemicellulose from the regenerated material (RM) were successfully achieved. The cellulose content of the RM could reach 99.16 ± 0.15%, which is the highest purity of cellulose extracted from the lignocellulose biomass in one step by IL solvent systems. The delignification rate could reach 97.56 ± 0.29% while the hemicellulose was completely removed in only 1 h after the cornstalk powder was dissolved in [Bmim]Cl–AS (the AS content was 1.5 wt%) at 100 °C. The result showed that the addition of AS not only improved the purity of cellulose in the RM but also increased its yield. The yield of cellulose increased from 19.94 ± 0.45% to 71.04 ± 0.78% after the addition of AS. As the mild fractionation conditions reduced consumption of energy greatly as well as that the additive was cheap and environmentally friendly, the SDDE might be able to provide a feasible path to achieve an efficient cellulose extraction from lignocellulose biomass. In addition, utilization of the lignocellulose biomass mostly focused on the preparation of bioethanol via hydrolysis and fermentation. This work provided an alternative that high purity cellulose derivatives and cellulose composites could be produced from the lignocellulose biomass.

Refractive index is one of the important physical properties, which is widely used in separation and purification. In this study, the refractive index data of ILs were collected to establish a comprehensive database, which included about 2138 pieces of data from 1996 to 2014. The Group Contribution-Artificial Neural Network (GC-ANN) model and Group Contribution (GC) method were employed to predict the refractive index of ILs at different temperatures from 283.15 K to 368.15 K. Average absolute relative deviations (AARD) of the GC-ANN model and the GC method were 0.179% and 0.628%, respectively. The results showed that a GC-ANN model provided an effective way to estimate the refractive index of ILs, whereas the GC method was simple and extensive. In summary, both of the models were accurate and efficient approaches for estimating refractive indices of ILs.

A mild oxidative esterification of various aromatic aldehydes by sulfate radical redox system was presented. In the reaction pathway exploration, the transiency of MeOSO3– was disclosed, which was generated from esterification between the in situ generated HSO4– and MeOH, a rate-limiting step in the process. More importantly, the selectivity-controlling step was represented by the subsequent nucleophilic displacement between MeOSO3– and aldehydes. The ionic oxidant 1a ((NH4)2S2O8) with more N–H numbers in the cation, as compared with 1c ((n-Bu4N)2S2O8) and 1d ((PyH)2S2O8), has better performance in the oxidative esterification of aldehydes.

A new series of soft materials were successfully achieved by a simple synthetic method in water. The coordination reactions of task-specific ionic liquid with different metal oxides were systematically investigated and analyzed. The obtained ten ionic liquid–metal complexes (ILMCs) were developed for efficient electrolytes for dye-sensitized solar cells (DSCs). ILMC-based DSCs exhibit superior photovoltaic performance and the remarkable increases in efficiencies with a multiple of 1.46–2.63 compared with an ionic liquid (IL) electrolyte without a metal center. The mechanism investigations clarified the influences of different metal centers on the conversion efficiencies of the corresponding devices. The high conductivity and diffusion coefficient of I3−, inhibited electron recombination and low charge transfer impedance contribute to the superior photovoltaic performance of ILMC electrolytes. The new concept, simple composition, high conductivity and conversion efficiency along with an easy fabrication method qualify the ILMC-based soft materials as promising high-efficient alternative electrolytes of DSCs.

The alkylation of isobutane with butene is an important refining process for the production of a complex mixture of branched alkanes, which is an ideal blending component for gasoline. The current catalysts used in industrial processes are concentrated H2SO4 and HF, which have problems including serious environmental pollution, equipment corrosion, potential safety hazard, high energy consumption in waste acid recycling, etc. Solid catalysts are another type of catalyst for this alkylation; however, they suffer from problems related to rapid deactivation. Ionic liquids (ILs) can be considered as catalysts of the third generation to replace traditional catalysts in isobutane/butene alkylation to produce clean oil. In this review, alkylation catalyzed by various kinds of acidic ILs, including Lewis acidic ILs (such as chloroaluminate ones) and ILs containing Brønsted acidic functional groups (e.g., –SO3H, [HSO4]−), is reviewed. The currently reported ILs used in the catalysis of isobutane alkylation and their corresponding catalytic activity are summarized and compared. This will help the readers to know what kinds of ILs are effective for the alkylation of isobutane with butene and to understand which factors affect the catalytic performance. The advantages of the catalysis of isobutane/butene alkylation by ILs include tunable acidity of the catalyst by varying the ion structure, limited solubility of the products in the IL phase and therefore easy separation of the alkylate from the catalyst, environmental friendliness, less corrosion of equipment, etc., thus making catalysis by ILs greener. The mechanism and kinetics of the alkylation catalyzed by ILs are discussed. Finally, perspectives and challenges of the isobutane/butene alkylation catalyzed by ILs are given.

AbstractA CoII/CF3COOH (TFA)-catalyzed oxidative esterification of aldehydes and alkanols by using tBuOOH as an oxidant is reported. A mechanistic investigation indicated that the oxidation reaction proceeded through the formation of a CoIII−OCH(OMe)R complex, followed by H-atom abstraction by an in-situ-generated tBuO. radical. The former kinetic step was thought to be the selectivity-determining step. Moreover, the strong acidity and TFA proton were beneficial for both the dehydrative formation of the CoIII−OCH(OMe)R complex and the redox properties of the cobalt atom, thereby offering high efficiency for the target oxidative cross-coupling reaction.

Ionic liquid coupled with strong acid systems presents considerable promise in some catalytic fields. In the present work, the multiple complex systems composed by 98 wt% concentrated sulfuric acid and [Bmim][SbF6] were investigated in the terms of stability, acidity and interaction properties. It was found that acidolysis of [Bmim][SbF6] occurred in the 98 wt% concentrated sulfuric acid accompanied by HF releasing and SbF6− degrading to [SbF6−y(HSO4)y]−. The species after acidolysis in the multiple complex systems were checked and confirmed by electrospray ionization mass spectrometry (ESI-MS), Fourier transform infrared spectroscopy (FT-IR), 1H NMR and 19F NMR. Acidity increased slightly with less than 1 wt% [Bmim][SbF6] addition, while decreased with more proportion, which was determined based on the Hammett acidity functions H0, using 13C NMR. The strong hydrogen bond S–O–H···F of interaction among the multiple complex systems was confirmed by molecular dynamic simulation.

It is critical for hypergolic fuels to be dense so as to enhance the performance of propellants and improve the loading of rockets. Considering that dense elements and bicyclic rings contribute to high density, two series of ionic liquids were prepared with 1-aza-bicyclo[2.2.2]octane-/1,4-diazabicyclo[2.2.2]octane-based cations and the dicyanamide anion. Their key properties were measured or calculated as decomposition temperature (208–322 °C), density (1.06–1.31 g cm−3), specific impulse (260.5 to 266.2 s) and ignition delay time (14–1053 ms). Compared with 1-aza-bicyclo[2.2.2]octane-based ionic liquids, the corresponding 1,4-diazabicyclo[2.2.2]octane-based ionic liquids exhibit a lower decomposition temperature, higher density and bigger specific impulse. As expected, 1-methyl-1-azonia-bicyclo[2.2.2]octane and 1-(prop-2-ynyl)-4-aza-1-azonia-bicyclo[2.2.2]octane dicyanamide possess higher densities (1.20 and 1.19 g cm−3) than the corresponding pyrrolidinium and imidazolium-based isomers (1.05 and 1.07 g cm−3), besides hypergolicity with white fuming nitric acid.

Membrane-based separation technology has been reported as one of the possible methods to efficiently and economically separate carbon dioxide (CO2). To provide synergistic enhancements in the gas separation performance, organic polymer (Pebax 1657), zeolite imidazolate framework-8 (ZIF-8) nanoparticles, and ionic liquid (IL) have been integrated to develop three-component composite membranes. To achieve high separation performance of three-component membranes, the effects of IL anions and ZIF-8 content on gas permeability and selectivity were investigated first. The ILs were 1-butyl-3-methyl imidazolium ([Bmim]) cation based on different anions of bis(trifluoromethylsulfonyl)imide ([NTf2]), dicyanamide ([DCA]), and tetrafluoroborate ([BF4]). Gas transport properties of all the prepared membranes were investigated at 23 °C and 1 bar. The results showed that the anion of IL is a key factor to determine the CO2 permeability of the membranes, which is similar to the principle of CO2 solubility in pure ILs. In addition, ZIF-8 could increase both CO2 diffusivity and solubility coefficients of the Pebax/ZIF-8 membranes, resulting in a two-fold increase in the CO2 permeability. For the Pebax/ZIF-8(15%)/[Bmim][NTf2] membranes, it has been revealed that [Bmim][NTf2] acts as a low molecular weight additive, leading to a more amorphous structure and a higher FFV (fractional free volume) of the membranes, which are beneficial for gas diffusion. The addition of IL can improve the compatibility between the inorganic particles and the polymer matrix; thus, the non-selective voids decrease, which leads to a higher CO2/N2 selectivity. The CO2 permeability of the Pebax/ZIF-8(15%)/IL(80%) membrane was 4.3 times that of the pure Pebax membrane without sacrificing the CO2/N2 selectivity. Therefore, the high gas transport properties of the Pebax/ZIF-8/IL membranes make them promising candidates for CO2-effective separation materials.

An increasing interest has been manifested in the use of ionic liquids (ILs) as solvents for the dissolution of wool keratin due to their tunable and excellent properties, despite the fact that it is still a challenge that ILs with different structures have distinct dissolution capabilities for wool. In this study, a series of 1,5-diazabicyclo[4.3.0]-non-5-ene (DBN)-based ionic liquids with different anions have been designed and employed for the dissolution of wool keratin. The effects of the ILs structures on their dissolution capabilities were systematically studied, and the optimal IL with high dissolution capability for goat wool was finally obtained by overall considering the time taken for the goat wool complete dissolution and the properties of the regenerated keratin. It was found that both cations and anions, acting as the regulators for polarity (ENT) and hydrogen-bond basicity (β) of the ILs, have significant influence on the dissolution capabilities of the ILs, which play an important role in the design and synthesis of new functional ILs for the dissolution of wool keratin. Furthermore, the time taken for the complete dissolution of 8 wt% goat wool in the optimum IL 1-ethyl-1,5-diazabicyclo[4.3.0]-non-5-enium diethylphosphate ([DBNE]DEP) is 3 h at 393 K, and the relative crystallinity, content of α-helix, and decomposition temperature of the regenerated keratin from [DBNE]DEP are higher (60.99%, 57.88%, and 521 K, respectively) than that from other ILs. Moreover, the break ratio of the disulfide bond is reduced to only 53.46%. In addition, [DBNE]DEP could be easily reused at least 5 times with stable structures and good dissolving ability, and the non-newtonian index, n, of the DEP IL/keratin solutions is all about 0.8, which means that the DEP IL/keratin solution has good prospects in terms of spinning.

•Copper can improve the catalytic performance of heteropolyoxometalates for oxidation reaction.•Cu2+ and Cu+ coordinate with 4 water molecules in the secondary structure of catalysts.•Copper can accelerate the re-oxidation process of active sites to improve the catalytic performance.Finding out the mechanism how copper improves the catalytic performance is important to design efficient heteropolyoxometalate catalysts for clean production of methacrylic acid. In this work, copper containing heteropolyoxometalate catalysts (CsCuxH3–2xPMo11VO40) were synthesized, characterized and used to catalyze the oxidation of methacrolein (MAL) to methacrylic acid. The FT-IR, TG-DTA and XPS results showed that copper was in the forms of Cu2+ and Cu+ and complexes with 4 water molecules in the secondary structure of the catalysts at room temperature. XRD and BET analysis showed that the addition of copper could increase the crystalline size of catalysts, prevent the accumulation of catalyst crystal and make catalysts to be a kind of mesoporous materials with narrow pore width distribution (around 4 nm), which is positive for the catalytic performance. The catalytic tests showed that the addition of copper can obviously improve the catalytic performance of catalysts. Copper can get an electron from Keggin structure to improve the oxidation ability of active sites during the oxidation of MAL and give an electron to Keggin structure to make the reduced active sites to be re-oxidized easily. This paper gives a clear picture of copper states in the heteropolyoxometalate catalysts and the mechanism how copper improves the performance of heteropolyoxometalate catalysts s for oxidation reactions.Download full-size image

A new route for deep hydrodenitrification (HDN) by solid catalyst coupling with ionic liquids (ILs) under mild conditions was proposed. Ni2P/SBA-15 activated at different temperatures were characterized with XRD, XPS, TG/DTA, and TEM and studied for further improvement. The deep HDN catalyzed by Ni2P/SBA-15 coupling with different ILs was evaluated. [Bmim]BF4 was selected as the best one compared with [Emim]BF4, [Bmim]Cl and [Bmim]Br. The effect of reaction temperature, hydrogen pressure and the amount of IL on denitrification efficiency was investigated with parallel experiments using Ni2P/SBA-15 coupling with [Bmim]BF4. The N-removal efficiency increased from 27.09% to 73.48% after optimization. The IL system could be recycled for three times without a significant decrease in HDN activity. The coupled catalyzed HDN process and mechanism were also proposed and evaluated preliminarily through molecular simulation.

A series of Cs(NH4)xH3–xPMo11VO40 with different x values were synthesized to catalyze the selective oxidation of methacrolein to methacrylic acid. The effects of ammonium on both structure and catalytic activity were explored in this study. Compared with CsH3PMo11VO40, the surface area, amount of acid sites, and active species (V4+/VO2+) were found to be strongly dependent on the content of ammonium. The optimum structure of Cs(NH4)1.5H1.5PMo11VO40 shows comparable large surface area of 50.33 m2/g, large amount of acid sites, and active species (V4+/VO2+), consequently offering a higher methacrolein conversion (83%) and methacrylic acid selectivity (93%). Furthermore, the steady activity of Cs(NH4)1.5H1.5PMo11VO40 was not affected much by the decomposition of ammonium, and the catalyst exhibited good stability.

Fe-doped HTaWO6 (H1−3xFexTaWO6, x = 0.23) nanotubes as highly active solid acid catalysts were prepared via an exfoliation–scrolling–exchange process. The specific surface area and pore volume of undoped nanotubes (20.8 m2 g−1, 0.057 cm3 g−1) were remarkably enhanced through Fe3+ ion-exchange (>100 m2 g−1, 0.547 cm3 g−1). Doping Fe ions into the nanotubes endowed them with improved thermal stability due to the stronger interaction between the intercalated Fe3+ ions and the host layers. This interaction also facilitated the preservation of effective Brønsted acid sites and the generation of new acid sites. The integration of these functional roles resulted in Fe-doped nanotubes with high acidic catalytic activities in the Friedel–Crafts alkylation of anisole and the esterification of acetic acid. Facile accessibility to active sites, generation of effective Brønsted acid sites, high stability of the tubular structure and strong acid sites were found to synergistically contribute to the excellent acidic catalytic efficiency. Additionally, the activity of cycled nanocatalysts can be easily recovered through annealing treatment.

Pomegranate-shaped Fe3O4/RGO nanohybrids were prepared via an ethylene glycol-mediated solvothermal method. Their morphology and structure were investigated by different characterization techniques. The red shift in FTIR and Raman spectra of nanohybrids demonstrated the existence of interfacial interactions between Fe3O4 and RGO. As anode material for lithium-ion battery, these nanohybrids exhibited elongated cycling stability and enhanced reversible capacity compared with bare Fe3O4 nanoparticles and mixture (Fe3O4 + RGO). The initial capacity of the nanohybrids could reach to 1266 mAh g−1 and remained 992 mAh g−1 after 100 cycles at 150 mAh g−1. Their cells manifested an outstanding rate capability of 384 mAh g−1 at 5.0 °C. The relationships between microstructure and performance were carefully exploited to obtain key factors that are helpful for design and construction of hybridized materials with improved electrochemical performance.

Four typical chloroaluminate ionic liquids (ILs) with different cations, namely 1-butyl-3-methylimidazoliumchloride [Bmim]Cl/AlCl3 (33.3/66.7 mol%), 1-butyl-3-methylpyridinium chloride [BMPyri]Cl/AlCl3 (33.3/66.7 mol%), 1-butyl-1-methylpyrrolidiniumchloride [Py1,4]Cl/AlCl3 (33.3/66.7 mol%), and trimethylphenylammonium chloride [TMPA]Cl/AlCl3 (33.3/66.7 mol%), were employed to deposit Al. The viscosity and ionic conductivity of these ILs were measured. The results showed that [Bmim]Cl/AlCl3 (33.3/66.7 mol%) had the lowest viscosity and the highest conductivity. Raman spectra showed that Al2Cl7− was the main anion in the four systems. Cyclic voltammetry indicated that [Bmim]Cl/AlCl3 (33.3/66.7 mol%) had the highest reduction current for Al deposition in the four ILs. By comparing the quality of the Al coatings prepared at the same current density and temperature, it was found that compact and smooth Al deposits could be obtained from [Bmim]Cl/AlCl3 (33.3/66.7 mol%) at 303 K, while the temperature needed was higher than 333 K for the other three ILs to obtain Al deposits with the same quality. Based on the density functional theory (DFT) calculations, the differences in these properties were attributed to the different molecular structure and cation-anion interaction induced by the cations of these ILs.

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A series of SiO2-confined Ru3(CO)12 catalysts for the water–gas shift (WGS) reaction was synthesized using a sol–gel method with five different 1-butyl-2,3-dimethylimidazolium ionic liquids (ILs) with BF4−, NO3−, Cl−, OTf−, and NTf2−. FT-IR, XRD, BET, SEM/EDS, TEM, ICP, CO-TPD and TGA were used to determine the influence of the different IL structures and loadings (10–40%) on the structure of the synthesized silica gel, Ru dispersion, and WGS catalytic activity. The results revealed that hydrogen bond formation capability and size of the anion of ILs have significant and sensitive effects. Catalytic activity was tested at atmospheric pressure and low reaction temperatures ranging from 120 to 200 °C. The highest CO conversion of 93.7% was achieved at 160 °C, which showed an around 100 °C decrease compared to traditional catalysts.

To produce basic chemicals from lignin, depolymerization and removal of oxygen from lignin through C–O cleavage and hydrodeoxygenation (HDO) are crucial steps. In this study, a novel, pseudo-homogeneous catalyst system, consisting of uniformly stabilized noble metal nanoparticles (NPs) in ionic liquids is developed for the selective reductive cleavage of C–O and HDO. Phenol and guaiacol as lignin monomer model compounds are investigated to gain an insight into the possible HDO pathway, meanwhile, dimeric model compounds such as diphenyl ether and benzyl phenyl ether are studied for the cleavage of C–O bonds between aromatic units. Four types of NPs including Pd, Pt, Rh and Ru were synthesized in situ and well distributed in ILs without aggregation. These catalytic systems displayed almost 100% conversion for various monomeric and dimeric lignin model compounds at 130 °C and were recycled several times without loss of activity. The catalytic selectivity of metals for HDO/C–O cleavage normally decreases in the order of Pt > Rh ∼ Ru ≫ Pd, which is similar to the order of NP size, Pd ≫ Pt > Rh ∼ Ru. With a mean diameter of 5.6 nm, Pt NPs in [Bmim]PF6 are identified as the best catalytic system for the transformation of lignin monomeric and dimeric model compounds with an almost 100% conversion and maximum 97% selectivity.

Ionic liquids (ILs) have many potential applications in the chemical industry. In order to understand ILs, their molecular details have been extensively investigated. Intuitively, electrostatic forces are solely important in ILs. However, experiments and calculations have provided strong evidence for the existence of H-bonds in ILs and their roles in the properties and applications of ILs. As a structure-directing force, H-bonds are responsible for ionic pairing, stacking and self-assembling. Their geometric structure, interaction energy and electronic configuration in the ion-pairs of imidazolium-based ILs and protic ionic liquids (PILs) show a great number of differences compared to conventional H-bonds. In particular, their cooperation with electrostatic, dispersion and π interactions embodies the physical nature of H-bonds in ILs, which anomalously influences their properties, leading to a decrease in their melting points and viscosities and thus fluidizing them. Using ILs as catalysts and solvents, many reactions can be activated by the presence of H-bonds, which reduce the reaction barriers and stabilize the transition states. In the dissolution of lignocellulosic biomass by ILs, H-bonds exhibit a most important role in disrupting the H-bonding network of cellulose and controlling microscopic ordering into domains. In this article, a critical review is presented regarding the structural features of H-bonds in ILs and PILs, the correlation between H-bonds and the properties of ILs, and the roles of H-bonds in typical reactions.

To develop a high-capacity, high-rate, cycle-stable cathode material has long been the focus for lithium-ion battery (LIB) research. Recently, layer-structured orthorhombic-LiMnO2 (o-LMO) has attracted extensive interest owing to its large discharge capacities. However, poor cycle performance greatly hinders its practical application, especially at high temperatures. Conventional strategies to address this issue often lead to sacrificed rate performance and mostly work at low temperatures. Herein, we report a novel core–shell structured, o-LiMnO2@Li2CO3 (o-LMO@Li2CO3) nanosheet array cathode, where the Li2CO3 shell improves cycle performance by preventing o-LMO dissolution in the electrolyte (even at an elevated temperature), the o-LMO core provides high capacities and the nanosheet array architecture ensures rate performance (to the best of our knowledge, this o-LMO nanosheet array architecture is reported for the first time). The above features work synergistically to give well-balanced cycle performance (79% capacity retention at 60 °C, 400 cycles), capacity (207 mAh g–1 at 0.5C) and rate performance (128 mAh g–1 at 5C) of the o-LMO@ Li2CO3 cathode as well as remarkable full-cell performance (∼67% capacity retention for 400 cycles at ∼2C, 60 °C). Our work demonstrates that the synergistic effect between the o-LMO core, Li2CO3 coating and the nanoarray structure is an effective strategy for developing high-energy/power density, high-stability LIB cathodes.

•Nanocomposites consisting of Ag2Se and hollow Pt nanoparticles are prepared.•The synthesis combines the in-side out diffusion of Ag with active Se species.•The nanocomposites have strong electronic coupling between Pt and Ag2Se domains.•The Ag2Se-hPt nanocomposites exhibit superior activity and stability for MOR.Making use of the electronic coupling between different domains in composite nanomaterials is an effective way to enhance the activity of electrocatalysts. Herein, we demonstrate the preparation of nanocomposites consisting of silver selenide (Ag2Se) and platinum (Pt) nanoparticles with a hollow interior by combining the inside-out diffusion of Ag in core-shell Ag-Pt nanoparticles with the synthesis of highly active hydrophobic Se species. In specific, the Ag2Se-hPt nanocomposites are found to have superior activity and stability for methanol oxidation reaction in an acidic condition due to the strong electronic coupling effect between semiconductor and metal domains. This strategy may provide a greener and less expensive way to the large-scale synthesis of Pt-based nanocomposites, and might be used to generate other heterogeneous nanomaterials with technological importance.

MgO, (NH4)2SO4 or MoO3-modified Ce0.6Zr0.4O2-supported gold catalysts were synthesized and studied for the oxidative esterification of methacrolein with methanol to methyl methacrylate. Although the particle size distribution and oxidative state of the supported Au showed almost no change before and after Ce0.6Zr0.4O2 modification as confirmed by TEM, Raman and XPS technologies, all of the modified Au/Ce0.6Zr0.4O2 catalysts demonstrated highly improved catalytic activities. H2-TPR patterns indicated that the amounts of low-temperature active oxygen species increased in the MgO- and MoO3-modified catalysts. At the same time, the strong interaction between gold and Ce–Zr oxides in the MgO-modified catalyst and the charge transfer between Mo6+ and Ce3+ in the MoO3-modified catalyst were evidenced by XPS characterization. Based on the enhanced synergetic effects between the Au nanoparticles and the support for oxygen activation, the MgO-promoted Au catalyst presented the best performance with a methacrolein conversion of 98% and a methyl methacrylate selectivity of 90% in the absence of a base at 80 °C for 2 h of reaction. Differing from MgO and MoO3, (NH4)2SO4 modification simultaneously increased the acid–base properties of the catalyst and then increased the activity of the catalyst due to the promoted formation of the intermediate hemiacetal.

•Catalytic pyrolysis of low rank coal was conducted by Ni based zeolite catalysts in the two-staged bed reactor.•The role of Ni based zeolite catalysts in the coal pyrolysis toward the pyrolysis gas yield and upgraded pyrolysis oil was investigated.•Yield of carbon oxides gases (CO, CO2) especially CO2 gas was decreased significantly as Ni loading increased in the catalysts.•The catalysts reduced the pitch contents in the pyrolysis oil and promoted the total fraction of light pyrolysis oils (BP < 360 °C).Pyrolysis is an important process in the coal conversion and has a significant effect on the distribution of volatile products. In this work, ZSM-5 zeolite with different Ni loading was studied to upgrade volatile matter using low rank coal (Shengli, Inner Mongolia) in the two-staged bed reactor. All prepared catalysts were characterized using X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) analysis and ammonia temperature-programmed desorption (NH3-TPD). The role of Ni metal loading toward the pyrolysis gas yield and upgraded pyrolysis oil was investigated. The yield of non-condensable gases decreases as Ni loading increased in the catalysts, especially the yield of CO2 decreased significantly. Moreover, the catalysts reduced the pitch contents in the pyrolysis oil and promoted the fraction of light pyrolysis oils (BP < 360 °C).

The efficient separation of CO2 from other light gases has received growing attentions due to its importance in reducing greenhouse gas emissions and applications in gas purification. In this work, we developed a series of composite membranes composed of ether-functionalized pyridinium-based ionic liquids ([EnPy][NTf2]) and cellulose acetate (CA) polymer matrices to improve CO2 separation performance. CA + [EnPy][NTf2] and CA + [CnPy][NTf2] composite membranes were fabricated by a casting method. The CO2, N2 and CH4 permeabilities of the CA + IL composite membranes were measured, and the CO2/N2 and CO2/CH4 permselectivities were further calculated. The results showed that the CA + 40 wt% [E1Py][NTf2] composite membrane exhibits approximately a seven-fold increase in CO2 permeability with CO2/N2 and CO2/CH4 permselectivities of 32 and 24, respectively. The characterization results showed that the mechanical properties and thermal stabilities of the CA + [E1Py][NTf2] composite membranes are affected by both plasticizing effect and affinity of the ILs for the gases, which also lead to the changes in the CO2/N2 and CO2/CH4 permselectivities. Compared with membranes containing the non-functionalized analogues [CnPy][NTf2], the addition of [EnPy][NTf2] improves the ideal permselectivities of CA + IL composite membranes, whereas it decreases slightly the gas permeabilities.

A double-layered Ge coated carbon cloth composite was synthesized by electrodepositing Ge from an ionic liquid using carbon cloth as substrate. As an integrated electrode, the composite exhibits a high initial charge capacity of 1169 mA h g−1 and retains 989 mA h g−1 after 100 cycles at 300 mA g−1.

Crystalline silicon (Si) is widely used in modern electronics. Si is commonly produced through a series of energy-intensive reactions (>700 °C). It is thus urgent and significant to explore more economically and environmentally-benign synthetic strategies for crystalline Si at low temperature. In this contribution, we report an efficient method to prepare crystalline Si from silicon tetrachloride at the low temperature of 100 °C with an ionic liquid (IL) as electrolyte. Physicochemical characterization revealed that as-deposited crystalline Si with a diamond cubic crystal structure exhibited a dominant (111)-orientation. Moreover, in-depth insights into the growth mechanism of crystalline Si was shed light upon herein. Furthermore, the smart electrodepositing platform of crystalline Si from ILs would open up a new avenue for low-temperature metallurgy of Si.

Phenolic compounds could be separated through their formation of deep eutectic solvent (DES). This process was different from normal liquid–liquid extraction and was more efficient and environmental. In this work, the thermodynamic process of this kind of separation was studied. Ternary liquid–liquid equilibrium data were systematically measured at atmospheric pressure and temperatures from 303.15 to 313.15 K. The experimental data were regressed by NRTL and UNIQUAC models, and the validated results revealed that NRTL model were more consistent with experimental data. The above-mentioned parameters could be used to predict ternary mixture interactions and then applied in subsequent design and optimization of the separation process of corresponding systems. This extraction process was further optimized using Aspen Plus with NRTL as thermodynamic model. The simulation results were in good agreement with the experimental outcomes.

Reaction distillation was first used for the process of acrylic acid synthesis through transesterification of methyl acrylate with acetic acid using a strongly acidic cationic exchange resin catalyst (NKC-9). Pseudo-homogeneous (P-H) and Langmuir–Hinshelwood (L-H) heterogeneous kinetic models were presented and fitted with the experimental data obtained from the batch reaction. The key factors of the heterogeneous kinetic model were the four components’ adsorption equilibrium constants on the catalyst surface, and they were determined by adsorption experiments. The activity coefficients were calculated using the NRTL method. The catalyst stability was evaluated in a fixed-bed reactor. Catalyst activity showed no obvious decrease after 1000 h of running. A reactive distillation column for acrylic acid synthesis was proposed and designed with process simulation.

Predicting hydrogen sulfide (H2S) solubility in ionic liquids (ILs) is vital for industrial gas desulphurization. In this work, the qualitative analysis of the influence of cations and anions on the H2S solubility in ILs has been conducted. The results indicate that anions play an important role in determining the H2S solubility in ILs. Subsequently, two novel quantitative structure–property relationship (QSPR) models are developed based on charge distribution area (Sσ-profile) descriptors and an extreme learning machine (ELM) algorithm. To develop the QSPR models, a total of 1282 pieces of data belonging to 27 ILs are employed to validate the models. The average absolute relative deviation (AARD%) and coefficient of determination (R2) of the two QSPR models of the entire data set are 3.73% and 0.998, as well as 3.80% and 0.997, respectively. These results suggest that the proposed QSPR models can be useful for the prediction of H2S solubility in ILs.

1,4-Cyclohexanedimethanol (CHDM) is a highly valued and widely used monomer in the polymer industry. Bis(2-hydroxyethylene terephthalate) (BHET), the product of glycolysis of waste PET, is an excellent raw material for the preparation of CHDM. Herein, a series of monometallic, bimetallic and trimetallic supported catalysts were prepared for the one-pot conversion of BHET into CHDM by the impregnation method and good performance was found over trimetallic RuPtSn/Al2O3 catalysts containing various active sites to catalyze the hydrogenation of the phenyl and carbonyl groups. The influences of various reaction parameters including temperature, pressure and time on the hydrogenation reaction were studied, and 100% conversion and 87.1% yield of CHDM were obtained with the trimetallic supported catalyst with Ru/Sn 1.5. Moreover, through the comparison between various methods for the preparation of CHDM, the conversion of BHET into CHDM by the one-pot method is considered one of the most competitive methods.

Layered inorganic–organic TiO2–ILs hybrids with tunable basal spacing were fabricated through electrostatic interaction between 2D inorganic nanosheets and organic imidazolium-based ILs. Imidazolium cations with various sizes were intercalated into lamellar titanate nanosheets, forming layered structures with slabs turbostratic restacking. The effects of cation sizes on the interfacial properties of hybrids were comprehensively investigated by XRD, SEM, TEM, AFM, FT-IR, Raman and TG techniques. The results confirmed that the ratio of interlayer imidazolium cations declined with increasing carbon chain length. A CO2 absorption experiment was conducted and TiO2–ILs compounds displayed enhanced CO2 absorption capacity with the increase of alkyl chain length, which could be attributed to the synergistic interfacial effects induced by diverse interactions between ILs and inorganic nanosheets. An absorption mechanism was proposed on account of ion-exchangeable characteristic of these layered hybrids and the intercalated H2O molecules were found to play a crucial role in CO2 uptake.

Developing lithium ion batteries (LIBs) with fast charging/discharging capability and high capacity is a significant issue for future technical requirements. Transition-metal oxide (TMO) materials are widely studied as the next-generation LIB anode to satisfy this requirement due to their specific capacity, nearly three times than that of conventional graphite anode, and low cost. Meanwhile, they also suffer from slow lithium diffusion and limited electrochemical and structural stability, especially at high charging/discharging rate. The structure design of TMO is an effective strategy to obtain desirable LIB performance. Herein, inspired by natural fibrous roots consisting of functional and supporting units that can enhance substances and energy exchange efficiently, fibrous-root-like ZnxCo3–xO4@Zn1–yCoyO binary TMO nanoarrays are designed and synthesized on Cu substrates through a facile one-pot, successive-deposition process for use as an integrated LIB anode. In a multilevel array ordered by orientation, ultrafine ZnxCo3–xO4 nanowire functional units and stable Zn1–yCoyO nanorod supporting units synergize, resulting in superior rate performance. At a high current density of 500 mAg–1, they could maintain a discharge capacity as high as 804 mAh g–1 after 100 cycles, working much higher than unary cobalt-based and zinc-based nanoarrays. This binary synergistic nanoarray system identifies an optimized electrode design strategy for advanced battery materials.Keywords: binary nanoarray; biomimetic material; hierarchical structure; lithium ion battery; synergistic system; transition-metal oxide;

It is urgent to develop a new deep desulfurization process of fuels as the environmental pollution increases seriously. In this work, a series of Lewis acidic ionic liquids (ILs) [C43MPy]Cl/nZnCl2 (n=1, 1.5, 2, 3) were synthesized and used in extraction and catalytic oxidative desulfurization (ECOD) of the fuels. The effects of the Lewis acidity of ILs, the molar ratio of H2O2/sulfur, temperatures, and different substrates including dibenzothiophene (DBT), benzothiophene (BT) and thiophene (TS), on sulfur removal were investigated. The results indicated that [C43MPy]Cl/3ZnCl2 presented near 100% DBT removal of model oil under conditions of 323 K, H2O2/DBT molar ratio 6:1. Kinetics for the removal of DBT, BT and TS by the [C43MPy]Cl/3ZnCl2-H2O2 system at 323 K is first-order with the apparent rate constants of 1.1348, 0.2226 and 0.0609 h-1, and the calculated apparent activation energies for DBT, BT and TS were 61.13, 60.66, and 68.14 kJ/mol from 298 to 308 K, respectively. After six cycles of the regenerated [CC43MPy]Cl/3ZnCl2, the sulfur removal had a slight decrease. [CC43MPy]Cl/3ZnCl2 showed a good desulfurization performance under optimal conditions.

Imidazolium-based ionic liquid [Cnmim]Br (n = 10, 12, 14) without any additives in aqueous solutions could form unilamellar vesicles was first observed by TEM recently. As molecular aggregation is a complex phenomenon which is difficult to study in detail experimentally, we performed molecular simulations for [Cnmim]Br (n = 10, 12, 14) aqueous solutions. The entire process of spontaneous aggregation for [C12mim]Br into small unilamellar vesicle was elucidated. Radial distribution functions reveal that the strong spatial correlation between cation and anion still exists in the presence of a large amount of water. The inner layer of vesicle is packed denser than the outer layer by analyzing the radial density distribution. Furthermore, anions distribution provides the direct evidence for very little anions being dissolved in the water and verifies the experimental speculation. By analyzing hydrogen bond number and coordination number in the solution, it is implied that binding between counterions enhanced with increasing IL concentration, and the distribution density of ions in vesicle is close to the neat system. Moreover, it is observed that aggregation is facilitated with increasing the alkyl chains by comparing three aqueous solution systems. Additionally, spatial correlation between chain terminal C becomes stronger with increasing the alkyl chain length.

Developing electrolyte with high electrochemical stability is the most effective way to improve the energy density of double layer capacitors (DLCs), and ionic liquid is a promising choice. Herein, a novel ionic liquid based high potential electrolyte with a stabilizer, succinonitrile, was proposed to improve the high potential stability of the DLC. The electrolyte with 7.5 wt% succinonitrile added has a high ionic conductivity of 41.1 mS cm-1 under ambient temperature, and the DLC adopting this electrolyte could be charged to 3.0 V with stable cycle ability even under a discharge current density of 6 A g-1. Moreover, the energy density could be increased by 23.4% when the DLC was charged to 3.0 V compared to that charged to 2.7 V.

Colloidal mesoporous magnetite nanoparticles with tunable porosity were realized by a simple and scalable solvothermal route with the aid of AOT as ligands. AOT was used to induce the anisotropic crystal growth of smaller nanocrystals and restrain their tight aggregation so as to form more mesoscale pores. Morphologies and microstructures investigation by SEM and TEM revealed that the bigger nanoparticles were composed of smaller nanocrystals with an average size of 18 nm. A possible formation mechanism was proposed for the mesoporous nanoparticles. Study of nitrogen adsorption–desorption isotherm revealed that the Brunauer–Emmett–Teller (BET) specific surface area of mesoporous nanoparticles is up to 209 m2/g, resulting from the slit-shaped pores created by the aggregation of polyhedral nanocrystals. Magnetic properties study indicated that the as-prepared nanoparticles are superparamagnetic at room temperature. Optimized mesoporous magnetite nanoparticles exhibit a maximum Cr(VI) ion sorption capacity of 12.9 mmol/g, and its absorption behavior followed a Freundlich model. Microwave absorption study indicated that porous nanoparticles own higher permeability values than that of solid nanoparticles, leading to a higher dielectric loss in the frequency range of 2–18 GHz.

Layered HNb3O8/graphene hybrids with numerous heterogeneous interfaces and hierarchical pores were fabricated via the reorganization of exfoliated HNb3O8 nanosheets with graphene nanosheets (GNs). Numerous interfaces and pores were created by the alternative stacking of HNb3O8 nanosheets with limited size and GNs with a buckling and folding feature. The photocatalytic conversation of CO2 into renewable fuels by optimized HNb3O8/G hybrids yields 8.0-fold improvements in CO evolution amounts than that of commercial P25 and 8.6-fold improvements than that of HNb3O8 bulk powders. The investigation on the relationships between microstructures and improved photocatalytic performance demonstrates that the improved photocatalytic performance is attributed to the exotic synergistic effects via the combination of enhanced specific BET surface area, increased strong acid sites and strong acid amounts, narrowed band gap energy, depressed electron–hole recombination rate, and heterogeneous interfaces.

A database and forecasting models of the solubility of hydrogen sulfide (H2S) in ionic liquids (ILs) are important for the industrial processes of gas sweetening. However, the specialized H2S solubility database and accurate predictive models are scarce at present. Therefore, this study first established a comprehensive database on the solubility of H2S in ILs, which includes 1334 pieces of data covering the period from 2007 to 2016. On the basis of the database, a new model is proposed using an extreme learning machine (ELM) intelligence algorithm and the number of fragments, which are easy to obtain and thus eliminate the need to use experimental data as input parameters. A total of 1282 pieces of data for 27 ILs (including 23 imidazolium-based and four ammonium-based ILs) have been used to build and test the model. The coefficient of determination (R2) and root-mean-square error (RMSE) of the ELM model for the test set are 0.990 and 0.0301, respectively. The results show that the established ELM model is applicable for predicting the solubility of H2S in ILs, which is important for the design, simulation, and analysis of new gas sweetening processes.

Deep eutectic solvents (DESs) have attracted broad attention due to their low cost, easy preparation, low toxicity, good biological compatibility and similar characteristics to those of ionic liquids (ILs). In this study, we found that not only the glycolysis time is sharply shortened under mild reaction conditions, but also the high selectivity of monomer bis(hydroxyalkyl) terephthalate (BHET) is obtained when DESs were used as catalysts. Then, the influences of technological parameters on PET degradation were investigated and the optimization conditions were obtained. Under the optimization conditions of ethylene glycol (EG) (20 g), catalyst (n(urea)/n(ZnCl2) 4/1, 0.25 g), PET (5 g), and atmospheric pressure at 170 °C for 30 min, the conversion of PET and selectivity of BHET were 100% and 83%, respectively. This time is equal to that taken by a supercritical method under 15.3 MPa at 450 °C. In addition, the degradation mechanism of PET wastes catalyzed by DESs is proposed through the experiments and DFT calculations. The high catalytic activity is attributed to the synergetic catalysis of H-bonds and coordination bonds formed between the DES catalyst and EG.

Conversion of biomass into gasoline of high octane number is challenging. In this study, conversion of biomass-derived γ-valerolactone into gasoline was achieved by decarboxylation of valerolactone to produce butenes and alkylation of the produced butenes with butane using [CF3CH2OH2][CF3CH2OBF3] as an efficient catalyst. The obtained gasoline was rich in trimethylpentane with a high research octane number of 95.4.

Correction for ‘An ionic liquid extraction process for the separation of indole from wash oil’ by Tiantian Jiao, et al., Green Chem., 2015, 17, 3783–3790.

A new type of magnetically recyclable solid acid catalyst was designed and retro-synthesized via a two-step template method. Magnetic Fe3O4 cores were synthesized by a solvothermal approach, and then coated with a silica layer by a sol–gel process in order to improve their stability in acid environments. HNbMoO6 nanosheets used as outer shell precursors were obtained by exfoliating a layered tri-rutile transition metal oxide (LiNbMoO6) via proton exchange and intercalation of tetrabutylammonium cations. Negatively charged nanosheets were assembled upon the Fe3O4@SiO2 particles using poly(diallyldimethylammonium chloride) as an opposite polyelectrolyte via a layer-by-layer sequential adsorption process. Protonation of the outer layer was realized by acid exchange treatment. The protonated core–shell nanocomposites showed effective catalytic properties for Friedel–Crafts alkylation reaction and high magnetic recyclability. These results highlight that the rational design and controllable synthesis of multifunctional catalysts is a promising strategy in “green chemistry” and “green technologies”.

A series of 4-R-5-nitro-1,2,3-triazolate salts (R = –CH3, –NH2, –NO2, –N3, and –NHNO2) were synthesized with cations of ammonium, hydroxylammonium, hydrazinium, guanidinium, aminoguanidinium, diaminoguanidinium, and triaminoguanidinium. The resulting energetic salts were characterized by 1H and 13C NMR, IR spectroscopy, elemental analysis, and in some cases by single crystal X-ray diffraction. Their key properties were measured or calculated such as melting and decomposition temperatures, density, detonation pressure and velocity, and impact and friction sensitivities. The results show that guanidinium salts possess the highest thermal stability in each group with decomposition temperatures of 265, 251, 221, 142, and 216 °C, respectively. Hydroxylammonium 4,5-dinitro-1,2,3-triazolate and dihydroxylammonium 4-nitramino-5-nitro-1,2,3-triazolate exhibit much higher detonation performances (38.0 GPa and 9302 m s−1; 38.8 GPa and 9464 m s−1) than cyclotrimethylenetrinitramine (34.9 GPa and 8748 m s−1). Moreover, the high specific impulses (256.1 and 251.1 s) from the formula calculations based on the two salts further support their application prospects.

First-row transition metal-containing ionic liquids (ILs) were synthesized and used to catalyze the degradation of poly(ethylene terephthalate) (PET) in ethylene glycol (EG). One important feature of these IL catalysts is that they have good thermal stability, and most of them, especially [bmim]2[CoCl4] (bmim = 1-butyl-3-methyl-imidazolium) and [bmim]2[ZnCl4], exhibit higher catalytic activity, compared with traditional catalysts, conventional IL catalysts, and some functional ILs. For example, utilizing [bmim]2[CoCl4] as catalyst, the conversion of PET, selectivity of bis(hydroxyethyl) terephthalate (BHET), and mass fraction of BHET in products reach up to 100%, 81.1%, and 95.7%, respectively, under atmospheric pressure at 175 °C for only 1.5 h. Another important feature is that BHET can be easily separated from these IL catalysts and has high purity. Moreover, recycling results show that [bmim]2[CoCl4] worked efficiently after being used six times. These all show that [bmim]2[CoCl4] is an excellent IL catalyst for the glycolysis of PET. Finally, based on in situ IR spectra and experimental results, the possible mechanism of degradation with synthesized IL is proposed.Keywords: Catalyze; Glycolysis; Mechanism; Poly(ethylene terephthalate); Transition metal-containing ionic liquids

A highly efficient Pd2Pb8/alumina catalyst was prepared, which provided the highest turnover number (TON) of 302 for aerobic oxidative coupling of methylacrolein with methanol. The enhanced catalytic efficiency could be attributed to the multi-scale (micron, nano and atom scales) promoting effects of the pre-loaded Pb species.

Au nanoparticles supported on Ce–Zr oxides were prepared and characterized in order to study the role of the support in the oxidative esterification of aldehydes in the presence of molecular oxygen. Ce–Zr solid solutions were synthesized by using (NH4)2Ce(NO3)6 as a precursor, while the mixed oxides were obtained by using a Ce(NO3)3 precursor. The solid solutions exhibited a smaller crystallite size, higher BET surface area, larger amount of H2 consumption, and higher acidity and basicity than the mixed oxides at the same Ce/Zr molar ratio due to the incorporation of Zr4+ into the ceria lattice. The effect of the support was investigated because all the samples presented similar Au particle sizes, as confirmed by the HAADF-STEM study. Supports with higher reducibility showed better performance by activating methanol to methoxy and facilitating the β-H elimination of hemiacetal. We also found that the formation of hemiacetal was enhanced by the acidic sites and basic sites of Au catalysts supported on solid solutions possessing similar reducibility. A plausible reaction mechanism for the oxidative esterification of aldehydes on Ce–Zr solid solution-supported Au nanoparticles was proposed. The screened catalyst was also applicable to the oxidative esterification of different benzylic aldehydes, producing high yields. This catalyst could be reused after a simple separation eight times, keeping a high selectivity of above 99%.

Potential applications of ILs require the knowledge of the physicochemical properties of ionic liquid (IL) mixtures. In this work, a series of semi-empirical models were developed to predict the density, surface tension, heat capacity and thermal conductivity of IL mixtures. Each semi-empirical model only contains one new characteristic parameter, which can be determined using one experimental data point. In addition, as another effective tool, artificial neural network (ANN) models were also established. The two kinds of models were verified by a total of 2304 experimental data points for binary mixtures of ILs and molecular compounds. The overall average absolute deviations (AARDs) of both the semi-empirical and ANN models are less than 2%. Compared to previously reported models, these new semi-empirical models require fewer adjustable parameters and can be applied in a wider range of applications.

In recent years, a variety of ionic liquids (ILs) were found to be capable of dissolving cellulose and mechanistic studies were also reported. However, there is still a lack of detailed information at the molecular level. Here, long time molecular dynamics simulations of cellulose bunch in 1-ethyl-3-methylimidazolium acetate (EmimAc), 1-ethyl-3-methylimidazolium chloride (EmimCl), 1-butyl-3-methylimidazolium chloride (BmimCl) and water were performed to analyze the inherent interaction and dissolving mechanism. Complete dissolution of the cellulose bunch was observed in EmimAc, while little change took place in EmimCl and BmimCl, and nothing significant happened in water. The deconstruction of the hydrogen bond (H-bond) network in cellulose was found and analyzed quantitatively. The synergistic effect of cations and anions was revealed by analyzing the whole dissolving process. Initially, cations bind to the side face of the cellulose bunch and anions insert into the cellulose strands to form H-bonds with hydroxyl groups. Then cations start to intercalate into cellulose chains due to their strong electrostatic interaction with the entered anions. The H-bonds formed by Cl− cannot effectively separate the cellulose chain and that is the reason why EmimCl and BmimCl dissolve cellulose more slowly. These findings deepen people's understanding on how ILs dissolve cellulose and would be helpful for designing new efficient ILs to dissolve cellulose.

In this study, two novel QSPR models have been developed to predict the viscosity of ionic liquids (ILs) using multiple linear regression (MLR) and support vector machine (SVM) algorithms based on Conductor-like Screening Model for Real Solvents (COSMO-RS) molecular descriptors (Sσ-profile). A total data set of 1502 experimental viscosity data points under a wide range of temperatures and pressures for 89 ILs, is employed to train and verify the models. The Average Absolute Relative Deviation (AARD) values of the total data set of the MLR and SVM are 10.68% and 6.58%, respectively. The results show that both the MLR and SVM models can predict the viscosity of ILs, and the performance of the nonlinear model developed using the SVM is superior to the linear model (MLR). Furthermore, the derived models also can throw some light onto structural characteristics that are related to the viscosity of ILs.

Deep eutectic solvents (DESs) have emerged as promising alternative candidates for CO2 capture in recent years. In this work, several novel DESs were firstly prepared to enhance CO2 absorption. Structural and physical properties of DESs were investigated, as well as their absorption performance of CO2. A distinct depression in the melting point up to 80 K of DESs was observed compared with that of BMIMCl. The observed red shifts of the C2H group in an imidazolium ring and its chemical shifts downfield in NMR spectra are indicative of a hydrogen bond interaction between BMIMCl and MEA. In particular, CO2 uptake in MEA:ILs (4:1) at room temperature and atmospheric pressure is up to 21.4 wt%, which is higher than that of 30 wt% MEA (13%). A hydrogen bond related mechanism was proposed in which ILs act as a medium to improve CO2 uptake through hydrogen bonds. Finally, the firstly reported overall heat of CO2 absorption is slightly higher than that of 30 wt% MEA, implying that the hydrogen bonds of DESs contribute to the overall heat of CO2 absorption. This study reveals that the heat of CO2 absorption can be tailored by the proper molar ratio of MEA and ILs.

Sulfur compounds in fuels have become one of the sources of serious environmental problems. The extractive desulfurization using ionic liquids (ILs) has attracted great attention in recent years. In this work, the pyridinium-based ionic liquids (ILs) N-butylpyridinium thiocyanate ([C4Py][SCN]), N-butylpyridinium bis(trifluoromethylsulfonyl)imide ([C4Py][NTf2]), and N-butylpyridinium dicyanamide ([C4Py][N(CN)2]) were used as extractants for desulfurization of model fuels. The results demonstrate that the structure of the anion influences the extractive performance of ILs, following the order of [NTf2] < [SCN] < [N(CN)2], which was proved by the electrostatic interaction between ions and DBT through molecular dynamics simulations (MD). In addition, the selectivity of sulfur compounds by the extraction process followed the order of dibenzothiophene (DBT) > benzothiophene (BT) > 4,6-dimethyldibenzothiophene (4,6-DMDBT). Moreover, the [C4Py][N(CN)2] can be recycled at least 4 times with little decrease in the desulfurization activity.

A new carbon-number-based kinetic model containing 18 hydrocarbon groups was developed in this work to describe coal tar hydrogenation, and the kinetic parameters were determined by means of fitting the experimental data, obtained in a two-stage fixed-bed reactor hydrogenation experiment, under various operating conditions. Model validation revealed that experimental data considerably agreed with expected outcomes. On this basis, a non-isothermal reactor model based on mass balance and energy balance as well as the proposed reaction kinetic model were constructed to further investigate the behavior of the hydrogenation fixed-bed unit, and the reactor model applied in a bench-scale plant of coal tar hydrogenation accurately simulated and predicted the yield distribution of carbon number products and the temperature profile along with the reactor. In addition, the entire process simulation for coal tar hydrogenation was developed using Aspen Plus. The simulation provided a significant guide for the optimization and design of industrial-scale hydrogenation.

In this work, the effect of SO2 on the densities and viscosities during absorption processes of pyridinium-based ionic liquids (ILs), such as the conventional ILs [C4Py][BF4] and [C4Py][SCN] and the tertiary amino-functionalized IL [NEt2C2Py][SCN], was investigated. The mechanism of the variations in these two physical properties was also explained in detail through a combination of experimental methods and simulation calculations. The results indicated that the densities of the conventional and functionalized ILs increased gradually with increasing amounts of SO2. However, the viscosities of two kinds of ILs during SO2 absorption showed different variation trends according to different mechanisms of SO2 absorption, i.e., physical absorption and chemical absorption, which was proven by the in situ Fourier transform infrared results. The viscosity changes of the functionalized IL [NEt2C2Py][SCN] during SO2 absorption experienced two stages. First, the viscosity increased sharply because of chemical interaction, forming a charge-transfer complex, and then decreased drastically because of the physical interaction between the anion and SO2. However, there was a monotonous and sharp decline in the viscosity of the conventional ILs with an increase of the SO2 capacity, which showed the same trend as that of [NEt2C2Py][SCN] in the SO2 physical absorption stage. Furthermore, the ionic interaction and microstructures of the conventional ILs before and after SO2 absorption were further studied by molecular dynamics simulation and quantum-chemical calculation. It was demonstrated that viscosity reduction may mainly originate from a decrease of the electrostatic interaction between the cation and anion of the ILs because of the presence of SO2.

In this work, we have prepared a 3D-composite-nanonetwork material consisting of a single walled carbon nanotube (SWNT) network and Si nanosphere embedded elements, through an electrostatic induced self-assembly process and the following film transfer technique. Negatively charged acid-functionalized SWNTs and positively charged surface-modified Si nanospheres composed a highly dispersed system, which was key to the fabrication of a self-assembled active material film. After transferring it to the Cu foil substrate by a novel film transfer technique, an integrated anode for lithium ion batteries (LIBs) was obtained without using binders or conductive additives, and exhibited excellent electrochemical performance. The continuous 3D conductive network consisting of SWNTs provided a rapid electronic transport pathway, which was able to counteract the conductivity decline caused by the formation of a solid electrolyte interface layer, thus ensuring a superior rate capability and cycling stability. This combined process of self-assembly and film transfer would provide a new idea for the design and preparation of LIB electrodes, especially those which are restricted by low conductivity and large volume change during cycling.

CL-20/graphene foam (GF) with a guest/host architecture was obtained by in situ crystallization of CL-20 in GF. With high detonation performance (44.1 GPa, 9687 m s−1), the CL-20/GF composite (98/2, w/w) is much less sensitive (IS: 4.5 J, FS: 252 N, ES: 0.72 J) than CL-20 (IS: 2.0 J, FS: 108 N, ES: 0.13 J).

In this work, three kinds of ether-functionalized pyridinium-based ILs [EnPy][NTf2] with low viscosity were designed and synthesized and used for highly selective separation of CO2 from CH4. It was found that the ether groups play an important role on physicochemical properties and CO2/CH4 selectivity in these three ILs. Compared with the nonfunctionalized analogues [CmPy][NTf2], the viscosities of [EnPy][NTf2] are lower and obviously decrease with the increasing number of ether oxygen atoms. The presence of ether groups on the cation has weak impacts on CO2 solubility of the ILs, but it contributes to a much lower CH4 solubility, which leads to the great increase of CO2/CH4 selectivity using [EnPy][NTf2]. Moreover, CO2/CH4 selectivity in all investigated ILs greatly decreases with the increasing temperature due to the weaker temperature dependence of CH4 solubility. In addition, the thermodynamic properties including the Gibbs free energy, enthalpy, and entropy of CO2 and CH4 in these ILs were also obtained, and the CO2 and CH4 dissolution mechanisms were further analyzed. The results demonstrated that the gas–IL interaction plays a dominate role in CH4 solubility in the investigated ILs, but CO2 dissolution in ILs is determined by both the IL–gas interaction and free volume of ILs. This work will offer new insights into designing more competitive ILs for selective separation of CO2 from CH4.

A synergistic effect of the hydrogen bond on the cycloaddition of CO2 and epoxides to form cyclic carbonates was investigated through experimental study and characterization. A highly effective homogeneous system of hydroxyl-functionalized quaternary ammonium ionic liquids with a different number of the hydroxyl group in the cation was developed for the fixation of CO2 to form cyclic carbonates. A mechanism via the hydrogen bond activation for the cycloaddition was proposed based on both experimental data and modeling. This research enhances the understanding of the promotion of reaction via hydrogen bonding and forms the basis for the rational design of catalytic systems for the fixation of CO2 into organic compounds.

The hydrogen-bond interactions in ionic liquids have been simply described by the conventional hydrogen-bond model of A-H⋯B. Coupling with the strong electrostatic force, however, hydrogen bond between the cation and anion shows particular features in the geometric, energetic, electronic, and dynamic aspects, which is inherently different from that of the conventional hydrogen bond. A general model could be expressed as +[A-H⋯B]−, in which A and B represent heavy atoms and “+” and “−” represent the charges of the cation containing A atom and anion containing B atom, respectively. Because the structure shows a “zig-zag” motif, this coupling interaction is defined here as the Z-bond. The new model could be generally used to describe the interactions in ionic liquids, as well as bio-systems involved in ions, ionic reaction, and ionic materials.

•The effect of IL on the synthesis of Pt-based nanoparticles has been investigated.•Core–shell Ag–Pt and Au–Pt nanoparticles have been prepared in the presence of IL.•IL has significant effect on the size/morphology of core–shell Ag–Pt nanoparticles.•IL mainly affects the electrochemical property of core–shell Au–Pt nanoparticles.Because of their many distinct advantages, the application of ionic liquids (ILs) for the synthesis and tailoring of nanoscale metal catalysts represents a burgeoning direction in materials chemistry. We herein depict the using of ammonium dibutyl phosphate ([AD]PO4), an organic soluble ionic liquid as an additive for the synthesis of Pt-based nanoparticles at elevated temperature in oleylamine. The experimental results reveal that not only the size/morphology, but also the electrocatalytic property of the platinum (Pt)-based bimetallic nanoparticles could be significantly tuned by a small amount of ionic liquid added in the reaction systems. For the silver (Ag)-Pt bimetallic system, core–shell Ag–Pt nanoparticles with dense or dendritic Pt shells are obtained at IL/oleylamine volume ratio of 0.25/10 and 0.5/10, while for gold (Au)-Pt bimetalic system, although the tuning of IL on the size/morphology of the particles are not apparent, the core–shell Au-Pt nanoparticles synthesized at IL/oleylamine volume ratio of 0.5/20 exhibit superior catalytic activity and durability for methanol oxidation reaction (MOR), compared to those prepared at other volume ratios.

A piperidinium-based ionic liquid, N-methylpiperidinium-N-acetate bis(trifluoromethylsulfonyl)imide ([MMEPip][TFSI]), was synthesized and used as an additive to the electrolyte of LiFePO4 battery. The electrochemical performance of the electrolytes based on different contents of [MMEPip][TFSI] has been investigated. It was found that the [MMEPip][TFSI] significantly improved the high-rate performance and cyclability of the LiFePO4 cells. In the optimized electrolyte with 3 wt% [MMEPip][TFSI], 70 % capacity can be retained with an increase in rate to 3.5 C, which was 8 % higher than that of electrolyte without [MMEPip][TFSI]. For the Li/LiFePO4 half-cells, after 100 cycles at 0.1 C, the discharge capacity retention was 78 % in the electrolyte without ionic liquid. However, in the electrolyte with 3 wt% [MMEPip][TFSI], it displayed a high capacity retention of 91 %. The good electrochemical performances indicated that the [MMEPip][TFSI] additive would positively enhance the electrochemical performance of LiFePO4 battery.

It is of crucial importance to form C–C bonds between biomass-derived compounds for the production of bio-alkanes from biomass. In this study, it was found that C–C bonds can be formed between angelica lactones, key intermediates derived from biomass, through free radical reactions under mild conditions without using a noble catalyst or solvent, which gave elongated carbon chains of di/trimers with 10 or 15 carbons, with complete conversion and 100% selectivity. The di/trimers produced serve as a novel feedstock for the carbon backbones of bio-alkanes. Hydrogenation of the di/trimers produced C6–C13 hydrocarbons suitable for use as transportation fuels.

As highlighted by the recent ChemComm web themed issue on ionic liquids, this field continues to develop beyond the concept of interesting new solvents for application in the greening of the chemical industry. Here some current research trends in the field will be discussed which show that ionic liquids research is still aimed squarely at solving major societal issues by taking advantage of new fundamental understanding of the nature of these salts in their low temperature liquid state. This article discusses current research trends in applications of ionic liquids to energy, materials, and medicines to provide some insight into the directions, motivations, challenges, and successes being achieved with ionic liquids today.

Herein, we report for the first time that a La–Mg composite oxide modified extra-large mesoporous FDU-12 supported Au–Ni bimetallic catalyst exhibits excellent performance for oxidative coupling of aldehydes (including benzyl and aliphatic aldehydes) with methanol to directly produce methyl esters.

Sulfur dioxide (SO2) emitted from the combustion of fossil flues is a major atmospheric pollutant that seriously threatens the environment and human health. The traditional methods for the removal and recovery of SO2 are irreversible and can result in secondary pollution or suffer from solvent loss. Therefore, it is urgent to explore new absorbents for the reversible, efficient, and environment-friendly capture of SO2. Ionic liquids (ILs) exhibit excellent performance for SO2 capture because of their unique physicochemical properties. To improve the absorption capacities of ILs for SO2, a series of novel ether-functionalized pyridinium chloride ILs ([EnPy]Cl, n = 2–4) were designed and synthesized. The physiochemical properties of these ILs and their SO2 absorption performance under different conditions were investigated. In addition, the SO2/CO2 selectivities and reusabilities of the ILs and the absorption mechanism between SO2 and [EnPy]Cl (n = 2–4) were studied. It was found that 1-[2-(2-methoxyethoxy)ethyl] pyridinium chloride showed a relatively high absorption capacity of up to 1.155 (g of SO2)·(g of IL)−1 at 20 °C and 0.1 MPa. The SO2 absorption capacities of the studied ILs remained steady in absorption–desorption cycles, implying that [EnPy]Cl (n = 2–4) could be promising candidates for SO2 capture.

Engineers often demand generalized models without sophisticated and long-time computations. To date, such models are still lacking for the density prediction of ionic liquid (IL) mixtures. In this paper, corresponding states principle combining with new mixing rules is employed to develop two new generalized models for density prediction of IL mixtures, including an extended Riedel (ER) model and an artificial neural network (ANN) model. A total of 1985 data points of binary and ternary mixtures of IL with molecular solvents, such as water, alcohols, ketones, ethers, hydrocarbons, esters, and acetonitrile, are used to verify the models. Average absolute relative deviations of the ER model and the ANN model are 0.92% and 0.37%, respectively, which indicates both the developed models can achieve a universal and accurate density prediction of IL mixtures. Moreover, the ER model does not contain any fitted parameters and thus provides a real predictive method.

Ionic liquid (IL)–amine hybrid solvents have been experimentally proved to be effective for CO2 capture. This Article provided rigorous thermodynamic models, process simulation, and cost estimation of a potential design of IL-based CO2 capture processes. Three ILs ([Bmim][BF4], [Bmim][DCA], and [Bpy][BF4]) were investigated to blend with MEA aqueous solution. The physicochemical properties of the ILs were predicted by several temperature-dependent correlations. Phase equilibria were modeled based on Henry’s law and NRTL equation, and the calculated values were in good agreement with the experimental data. The simulation results show that the [Bpy][BF4]–MEA process can save about 15% regeneration heat duty as compared to the conventional MEA process, which is attributed to the reduction of sensible and latent heat. Moreover, a modified [Bpy][BF4]–MEA process via adding intercooling and lean vapor recompression presents 12% and 13.5% reduction in overall equivalent energy penalty and capture cost as compared to the conventional MEA process, respectively.

The synthesis of noble metal nanoparticles (NMNPs) using, or in the presence of, ionic liquids (ILs) represents a burgeoning direction in materials chemistry. Processing these nanomaterials synthesized in ILs would be drastically simplified if they could be routinely dispersed into a wide variety of polar/nonpolar solvents. We herein demonstrate the phase transfer of the as-prepared nanoparticles from ILs to an organic or aqueous medium. The protocol involves first mixing the noble metal sols in ILs and an ethanolic or a methanolic solution of transfer agent and then extracting the transfer-agent-stabilized NMNPs into toluene or aqueous phase. Electron micrographs reveal that the particles are fully dispersed after transfer, and the size/morphology of the NMNPs could be significantly tuned by the ILs. In particular, electrochemical measurements of the Pt nanoparticles upon methanol oxidation reaction demonstrate that the particles are dominated by low-index crystal planes.

Ionic liquids (ILs) have attracted many attentions in the dissolution of cellulose due to their unique physicochemical properties as green solvents. However, the mechanism of dissolution is still under debate. In this work, computational investigation for the mechanisms of dissolution of cellulose in [Bmim]Cl, [Emim]Cl and [Emim]OAc ILs was performed, and it was focused on the process of breakage of cellulose chain and ring opening using cellobiose as a model molecule. The detailed mechanism and reaction energy barriers were computed for various possible pathways by density functional theoretical method. The key finding was that ILs catalyze the dissolution process by synergistic effect of anion and cation, which led to the cleavage of cellulose chain and formation of derivatives of cellulose. The investigation on ring opening process of cellobiose suggested that carbene formed in ILs played an important role in the side reaction of cellulose, and it facilitated the formation of a covalent bond between cellulose and imidazolium core. These computation results may provide new perspective to understand and apply ILs for pretreatment of cellulose.The mechanism of dissolution of cellulose in ionic liquids (ILs) was investigated by density functional theoretical method. ILs would lead to the cleavage of cellulose chain by synergistic effect of anion and cation. The acetate-based ILs can form N-heterocyclic carbene, which will facilitate the ring opening reaction to form a covalent bond between cellulose and imidazolium core.Download full-size image

•Heteropoly catalysts with core-shell structure showed best catalytic performance for oxidation of methacrolein to methacrylic acid.•The properties of core-shell structured catalysts can be tuned by changing thermal treatment temperature and time of Cs4PMo11VO40.•The byproduct selectivity was mainly controlled by the acidity of catalysts.A series of novel heteropoly catalysts (H4PMo11VO40/Cs4PMo11VO40) with core shell structure were designed and synthesized for effective oxidation of methacrolein to methacrylic acid. The effects of H4PMo11VO40 supporting amount on catalytic properties were investigated. With the hydrothermal treatment temperature increased from 25 to 180 °C, the surface area of Cs4PMo11VO40 decreased from 123.6 to 7.7 m2 g−1, while the acidity and oxidation susceptibility of Cs4PMo11VO40 were enhanced due to its re-crystallization. The XRD results showed that the crystalline form of H4PMo11VO40 changed from triclinic to cubic form because of the guidance effect of Cs4PMo11VO40. BET, NH3-TPD and XPS results indicated that compared with bulk H4PMo11VO40, surface area and oxidation susceptibility of the supported one increased significantly, and the acidity decreased. The sui thickness of H4PMo11VO40 layer on Cs4PMo11VO40 was a key point to tune the surface area, oxidation susceptibility and acidity of catalysts. At 310 °C, the methacrolein conversion and methacrylic acid selectivity on the optimum supported catalyst were more than 85% and 75%, respectively, which were much better than those on bulk H4PMo11VO40 (39% and 46%), Cs4PMo11VO40 (15.6% and 0%) and Cs2.6H1.4PMo11VO40 (99.9% and 36.5%).Download full-size image

•The mechanism of amino-functionalized imidazolium-based IL for fixation of CO2.•The mechanism catalyzed by multi-species is considered.•Positive charge is not the sole item to determine the electrophilic attack.•Ring-opening is promoted by both weak interaction and electrostatic interaction.The mechanism of coupling reaction of CO2 with propylene oxide (PO) catalyzed by the amino-functionalized imidazolium-based ionic liquid is theoretically investigated by the density functional theory (DFT). Although the mechanisms of the fixation of CO2 catalyzed by various room-temperature ionic liquids or functionalized ionic liquids have been theoretically elucidated in previous literatures, it is not totally suitable for the amino-functionalized ionic liquid. First, the 1-(3-aminopropyl)-3-methylimidazolium chloride ([APmim]Cl) would react with CO2 to produce the 1-(3-carbamic acid propyl)-3-methylimidazolium chloride ([CAPmim]Cl). Then, [APmim]Cl, [CAPmim]Cl, and combination of them would be employed as the catalyst leading to nine possible routes. Different from the previous work, this work allows a better comprehension of the mechanism by means of a new model that the cooperative effect of two same or different components is considered. Both the interaction between catalyst and reactant and the influence between different catalytic components are considered. Besides the nucleophilic attack of the Cl− anion, the [CAPmim]+ cation is taken as the main component to activate the O atom of PO directly leading to the ring-opening. The [APmim]+ cation is utilized to stabilize the [CAPmim]+, which is the most favorable route. The noncovalent interactions (NCI) plot is employed as a tool to analyze the reason of the higher catalytic efficiency of top three favorable routes. The hydrogen bond and dispersive attractive interaction is confirmed to play a determining role in the catalytic activity.Download high-res image (106KB)Download full-size image

•Synthesis of propylene glycol methyl ether was investigated over ionic liquids (ILs).•The basicity and Kamlet-Taft parameters for ILs were estimated.•Basicity of ILs is mainly determined by the nature of anion.•Correlation between basicity/hydrogen bond properties- catalytic performance of ILs was studied.The relationship of basicity and hydrogen bond with catalytic performance was investigated in synthesis of propylene glycol methyl ether (PGME) catalyzed by various ILs ([Emim][OAC], [Bmim][OAC], [N2222][OAC], [EtOHN111][OAC], [N4444]Br, [Bmim][N(CN)2], [Bmim]Br, [Bmim][PF6]). The basicity and Kamlet-Taft parameters of each catalyst were evaluated by UV–visible spectroscopy. It was found the catalytic performance is the synergistic effect of basicity and hydrogen bond donating ability in the synthesis of PGME from PO and CH3OH, which is quite different from the conventional basic catalytic mechanism.The correlation between basicity, hydrogen bond properties and catalytic performance of ionic liquids was studied in synthesis of propylene glycol methyl ether (PGME).Download high-res image (125KB)Download full-size image

Separation of products from ionic liquid (IL) solvents is one of the main challenges that hinder their utilizations. In this study, the production of γ-valerolactone (GVL) by selective hydrogenation of α-angelica lactone (AL) and separation of the products from the IL solvent were carried out by using subcritical CO2 as a “switch” at room temperature. After the mixture was separated into two phases by subcritical CO2, AL and nano Pd/C catalyst were only found in the lower IL-rich phase, GVL was produced with quantitative yield and enriched in the upper methanol-rich phase. Pure GVL can be obtained by depressurizing to release CO2 and evaporation to remove methanol of the upper phase, the lower phase containing IL, catalyst and methanol can be recycled for the next reaction. The strategy may provide a new approach to produce and separate products from IL solvents at mild conditions.

A small aggregate is composed of several or tens of molecules or ions, with at least one dimension in the range from a few to dozens of angstroms. Here, we named such aggregate system as Angstrom Aggregates (AA). AA with the specific size in angstrom meter might possess unique structure activity relationship. Unlike molecular level, nano system and the bulk, AA, an aggregate in angstrom scale is firstly proposed, its arrangement in order, electronic effect, surface interaction, confinement effect, is still unclear. However, recently, the structure and activity relationship of such aggregate in angstrom scale has attracted increasing interest in many areas, such as in ionic liquids, aqueous solution, catalytic system, and bio-system. As the physical and chemical propeties of AA strongly depends on its structure, the in situ characterization technique combined with theoretical methods should be developed to understand the exact interaction between the component of the clusters, the assembly formations, the special features, and the reaction activities. It has great scientific meaning to detect, represent and regulate the structure and function of AA precisely, facilitating in its application. A systematic and thorough research on AA in angstrom scale will promote the development of fundamental science and the progress of technology significantly.

•The MEL-GO was prepared by graphene oxide functionalized with melamine molecule.•A high efficient solid-liquid absorbent for CO2 absorption was designed and test by vapor-liquid equilibrium apparatus.•The enhance effect of the MEL-GO to the CO2 absorption were discussed.In this work, we have developed a highly efficient approach to fabricating graphene oxide (GO) functionalized with melamine molecule by chemical crosslinking. The melamine-functionalized graphene oxide (MEL-GO) was characterized by FT-IR, Raman, XRD TGA, XPS, SEM and TEM. Using monoethanolamine (MEA) aqueous solution as the basic absorbent, The absorbance performance of CO2 in the (MEL-GO)+MEA+H2O solid-liquid hybrid absorbent for different mass concentrations of MEL-GO in 30 wt% MEA aqueous solution was investigated. The solubility of CO2 in (MEL-GO)+MEA+H2O absorbents is much larger than that in 30 wt% MEA aqueous solution. Moreover, when the partial pressure of CO2 continues to go up, the solubility of CO2 was obviously increased with increasing mass concentrations of MEL-GO. The results suggest that MEL-GO is beneficial to enhance the solubility of CO2 in MEA aqueous solution.A highly efficient method can fabricate solid-liquid hybrid CO2 absorbent that consisted of amine-functionalized of graphene oxide (MEL-GO) and monoethanolamine (MEA) aqueous solution.

MgO, (NH4)2SO4 or MoO3-modified Ce0.6Zr0.4O2-supported gold catalysts were synthesized and studied for the oxidative esterification of methacrolein with methanol to methyl methacrylate. Although the particle size distribution and oxidative state of the supported Au showed almost no change before and after Ce0.6Zr0.4O2 modification as confirmed by TEM, Raman and XPS technologies, all of the modified Au/Ce0.6Zr0.4O2 catalysts demonstrated highly improved catalytic activities. H2-TPR patterns indicated that the amounts of low-temperature active oxygen species increased in the MgO- and MoO3-modified catalysts. At the same time, the strong interaction between gold and Ce–Zr oxides in the MgO-modified catalyst and the charge transfer between Mo6+ and Ce3+ in the MoO3-modified catalyst were evidenced by XPS characterization. Based on the enhanced synergetic effects between the Au nanoparticles and the support for oxygen activation, the MgO-promoted Au catalyst presented the best performance with a methacrolein conversion of 98% and a methyl methacrylate selectivity of 90% in the absence of a base at 80 °C for 2 h of reaction. Differing from MgO and MoO3, (NH4)2SO4 modification simultaneously increased the acid–base properties of the catalyst and then increased the activity of the catalyst due to the promoted formation of the intermediate hemiacetal.

A highly efficient Pd2Pb8/alumina catalyst was prepared, which provided the highest turnover number (TON) of 302 for aerobic oxidative coupling of methylacrolein with methanol. The enhanced catalytic efficiency could be attributed to the multi-scale (micron, nano and atom scales) promoting effects of the pre-loaded Pb species.

A series of 4-R-5-nitro-1,2,3-triazolate salts (R = –CH3, –NH2, –NO2, –N3, and –NHNO2) were synthesized with cations of ammonium, hydroxylammonium, hydrazinium, guanidinium, aminoguanidinium, diaminoguanidinium, and triaminoguanidinium. The resulting energetic salts were characterized by 1H and 13C NMR, IR spectroscopy, elemental analysis, and in some cases by single crystal X-ray diffraction. Their key properties were measured or calculated such as melting and decomposition temperatures, density, detonation pressure and velocity, and impact and friction sensitivities. The results show that guanidinium salts possess the highest thermal stability in each group with decomposition temperatures of 265, 251, 221, 142, and 216 °C, respectively. Hydroxylammonium 4,5-dinitro-1,2,3-triazolate and dihydroxylammonium 4-nitramino-5-nitro-1,2,3-triazolate exhibit much higher detonation performances (38.0 GPa and 9302 m s−1; 38.8 GPa and 9464 m s−1) than cyclotrimethylenetrinitramine (34.9 GPa and 8748 m s−1). Moreover, the high specific impulses (256.1 and 251.1 s) from the formula calculations based on the two salts further support their application prospects.

Au nanoparticles supported on Ce–Zr oxides were prepared and characterized in order to study the role of the support in the oxidative esterification of aldehydes in the presence of molecular oxygen. Ce–Zr solid solutions were synthesized by using (NH4)2Ce(NO3)6 as a precursor, while the mixed oxides were obtained by using a Ce(NO3)3 precursor. The solid solutions exhibited a smaller crystallite size, higher BET surface area, larger amount of H2 consumption, and higher acidity and basicity than the mixed oxides at the same Ce/Zr molar ratio due to the incorporation of Zr4+ into the ceria lattice. The effect of the support was investigated because all the samples presented similar Au particle sizes, as confirmed by the HAADF-STEM study. Supports with higher reducibility showed better performance by activating methanol to methoxy and facilitating the β-H elimination of hemiacetal. We also found that the formation of hemiacetal was enhanced by the acidic sites and basic sites of Au catalysts supported on solid solutions possessing similar reducibility. A plausible reaction mechanism for the oxidative esterification of aldehydes on Ce–Zr solid solution-supported Au nanoparticles was proposed. The screened catalyst was also applicable to the oxidative esterification of different benzylic aldehydes, producing high yields. This catalyst could be reused after a simple separation eight times, keeping a high selectivity of above 99%.

Ionic liquids (ILs) have many potential applications in the chemical industry. In order to understand ILs, their molecular details have been extensively investigated. Intuitively, electrostatic forces are solely important in ILs. However, experiments and calculations have provided strong evidence for the existence of H-bonds in ILs and their roles in the properties and applications of ILs. As a structure-directing force, H-bonds are responsible for ionic pairing, stacking and self-assembling. Their geometric structure, interaction energy and electronic configuration in the ion-pairs of imidazolium-based ILs and protic ionic liquids (PILs) show a great number of differences compared to conventional H-bonds. In particular, their cooperation with electrostatic, dispersion and π interactions embodies the physical nature of H-bonds in ILs, which anomalously influences their properties, leading to a decrease in their melting points and viscosities and thus fluidizing them. Using ILs as catalysts and solvents, many reactions can be activated by the presence of H-bonds, which reduce the reaction barriers and stabilize the transition states. In the dissolution of lignocellulosic biomass by ILs, H-bonds exhibit a most important role in disrupting the H-bonding network of cellulose and controlling microscopic ordering into domains. In this article, a critical review is presented regarding the structural features of H-bonds in ILs and PILs, the correlation between H-bonds and the properties of ILs, and the roles of H-bonds in typical reactions.

Lithium–sulfur suspension flow batteries are a promising technology for large-scale energy storage, but long-term stability of the suspension catholyte is urgently needed for future application of this system. Here a special self-stabilized suspension catholyte is designed and prepared based on a pie-structured sulfur-Ketjenblack@reduced graphene oxide (S-KB@rGO) composite. In the S-KB@rGO suspension, the sulfur nanoparticles are loaded onto the conductive KB by an in situ redox reaction; the special hyperbranched structure of KB enhances the stability of the suspension; rGO sheets which wrap the S-KB particles not only act as a multilayered physical barrier for sulfur immobilization, but also facilitate electron transportation in the whole suspension. Therefore, a suspension catholyte with long-term physical and electrochemical stability is achieved by the synergetic effect of the KB and rGO. Li–S flow cells with this catholyte show excellent cycle stability (more than 1000 cycles with 99% coulombic efficiency) and low self-discharge (1.1% loss per day). Continuous charge/discharge tests in different flow modes are performed and the influence of the flow rate on the flow battery performance is discussed. The smooth operation in long-lasting flow mode further demonstrates the stability of the suspension catholyte.

A new series of soft materials were successfully achieved by a simple synthetic method in water. The coordination reactions of task-specific ionic liquid with different metal oxides were systematically investigated and analyzed. The obtained ten ionic liquid–metal complexes (ILMCs) were developed for efficient electrolytes for dye-sensitized solar cells (DSCs). ILMC-based DSCs exhibit superior photovoltaic performance and the remarkable increases in efficiencies with a multiple of 1.46–2.63 compared with an ionic liquid (IL) electrolyte without a metal center. The mechanism investigations clarified the influences of different metal centers on the conversion efficiencies of the corresponding devices. The high conductivity and diffusion coefficient of I3−, inhibited electron recombination and low charge transfer impedance contribute to the superior photovoltaic performance of ILMC electrolytes. The new concept, simple composition, high conductivity and conversion efficiency along with an easy fabrication method qualify the ILMC-based soft materials as promising high-efficient alternative electrolytes of DSCs.

Refractive index is one of the important physical properties, which is widely used in separation and purification. In this study, the refractive index data of ILs were collected to establish a comprehensive database, which included about 2138 pieces of data from 1996 to 2014. The Group Contribution-Artificial Neural Network (GC-ANN) model and Group Contribution (GC) method were employed to predict the refractive index of ILs at different temperatures from 283.15 K to 368.15 K. Average absolute relative deviations (AARD) of the GC-ANN model and the GC method were 0.179% and 0.628%, respectively. The results showed that a GC-ANN model provided an effective way to estimate the refractive index of ILs, whereas the GC method was simple and extensive. In summary, both of the models were accurate and efficient approaches for estimating refractive indices of ILs.

A highly efficient synthesis of isosorbide from sorbitol was developed using Brønsted acidic ionic liquids (BILs) as the catalyst for the first time. The structure–performance relationship was discussed extensively and a proper value of the Gutmann acceptor number (AN) rather than the inherent of acidity was found to be essential for an optimized yield of isosorbide. In addition, the excellent behavior of preferred BIL-4 in the consecutive recycling tests renders the construction of a continuous process probable. Systematic optimization demonstrated that a yield of 82% of isosorbide with a purity of 99.3% could be reached at balance.

As highlighted by the recent ChemComm web themed issue on ionic liquids, this field continues to develop beyond the concept of interesting new solvents for application in the greening of the chemical industry. Here some current research trends in the field will be discussed which show that ionic liquids research is still aimed squarely at solving major societal issues by taking advantage of new fundamental understanding of the nature of these salts in their low temperature liquid state. This article discusses current research trends in applications of ionic liquids to energy, materials, and medicines to provide some insight into the directions, motivations, challenges, and successes being achieved with ionic liquids today.

Deep eutectic solvents (DESs) have emerged as promising alternative candidates for CO2 capture in recent years. In this work, several novel DESs were firstly prepared to enhance CO2 absorption. Structural and physical properties of DESs were investigated, as well as their absorption performance of CO2. A distinct depression in the melting point up to 80 K of DESs was observed compared with that of BMIMCl. The observed red shifts of the C2H group in an imidazolium ring and its chemical shifts downfield in NMR spectra are indicative of a hydrogen bond interaction between BMIMCl and MEA. In particular, CO2 uptake in MEA:ILs (4:1) at room temperature and atmospheric pressure is up to 21.4 wt%, which is higher than that of 30 wt% MEA (13%). A hydrogen bond related mechanism was proposed in which ILs act as a medium to improve CO2 uptake through hydrogen bonds. Finally, the firstly reported overall heat of CO2 absorption is slightly higher than that of 30 wt% MEA, implying that the hydrogen bonds of DESs contribute to the overall heat of CO2 absorption. This study reveals that the heat of CO2 absorption can be tailored by the proper molar ratio of MEA and ILs.

In recent years, a variety of ionic liquids (ILs) were found to be capable of dissolving cellulose and mechanistic studies were also reported. However, there is still a lack of detailed information at the molecular level. Here, long time molecular dynamics simulations of cellulose bunch in 1-ethyl-3-methylimidazolium acetate (EmimAc), 1-ethyl-3-methylimidazolium chloride (EmimCl), 1-butyl-3-methylimidazolium chloride (BmimCl) and water were performed to analyze the inherent interaction and dissolving mechanism. Complete dissolution of the cellulose bunch was observed in EmimAc, while little change took place in EmimCl and BmimCl, and nothing significant happened in water. The deconstruction of the hydrogen bond (H-bond) network in cellulose was found and analyzed quantitatively. The synergistic effect of cations and anions was revealed by analyzing the whole dissolving process. Initially, cations bind to the side face of the cellulose bunch and anions insert into the cellulose strands to form H-bonds with hydroxyl groups. Then cations start to intercalate into cellulose chains due to their strong electrostatic interaction with the entered anions. The H-bonds formed by Cl− cannot effectively separate the cellulose chain and that is the reason why EmimCl and BmimCl dissolve cellulose more slowly. These findings deepen people's understanding on how ILs dissolve cellulose and would be helpful for designing new efficient ILs to dissolve cellulose.

Potential applications of ILs require the knowledge of the physicochemical properties of ionic liquid (IL) mixtures. In this work, a series of semi-empirical models were developed to predict the density, surface tension, heat capacity and thermal conductivity of IL mixtures. Each semi-empirical model only contains one new characteristic parameter, which can be determined using one experimental data point. In addition, as another effective tool, artificial neural network (ANN) models were also established. The two kinds of models were verified by a total of 2304 experimental data points for binary mixtures of ILs and molecular compounds. The overall average absolute deviations (AARDs) of both the semi-empirical and ANN models are less than 2%. Compared to previously reported models, these new semi-empirical models require fewer adjustable parameters and can be applied in a wider range of applications.

A new type of magnetically recyclable solid acid catalyst was designed and retro-synthesized via a two-step template method. Magnetic Fe3O4 cores were synthesized by a solvothermal approach, and then coated with a silica layer by a sol–gel process in order to improve their stability in acid environments. HNbMoO6 nanosheets used as outer shell precursors were obtained by exfoliating a layered tri-rutile transition metal oxide (LiNbMoO6) via proton exchange and intercalation of tetrabutylammonium cations. Negatively charged nanosheets were assembled upon the Fe3O4@SiO2 particles using poly(diallyldimethylammonium chloride) as an opposite polyelectrolyte via a layer-by-layer sequential adsorption process. Protonation of the outer layer was realized by acid exchange treatment. The protonated core–shell nanocomposites showed effective catalytic properties for Friedel–Crafts alkylation reaction and high magnetic recyclability. These results highlight that the rational design and controllable synthesis of multifunctional catalysts is a promising strategy in “green chemistry” and “green technologies”.

In this study, two novel QSPR models have been developed to predict the viscosity of ionic liquids (ILs) using multiple linear regression (MLR) and support vector machine (SVM) algorithms based on Conductor-like Screening Model for Real Solvents (COSMO-RS) molecular descriptors (Sσ-profile). A total data set of 1502 experimental viscosity data points under a wide range of temperatures and pressures for 89 ILs, is employed to train and verify the models. The Average Absolute Relative Deviation (AARD) values of the total data set of the MLR and SVM are 10.68% and 6.58%, respectively. The results show that both the MLR and SVM models can predict the viscosity of ILs, and the performance of the nonlinear model developed using the SVM is superior to the linear model (MLR). Furthermore, the derived models also can throw some light onto structural characteristics that are related to the viscosity of ILs.