Construction of versatile multijunctions with visible light response, effective charges transport and separation, suitable band positions, and good stability is highly expected for the photocatalytic VOCs degradation. Herein, one-dimensional titania nanotube supported SrTiO3 heterostructure (STO/TN) was developed by a hydrothermal process and then simultaneously sensitized with carbon nitride polymer (CN) and doped with nitrogen (CN-STO/TN) for photocatalytic mineralization of toluene. CN-STO/TN simultaneously exhibits the following advantages: (1) the nanotube structure enhances light-harvesting, enables effective charges transport and separation, retains sufficient energy of the charges, facilitates the pollutant species transport and reactants enrichment by the confinement effect; (2) synergistic effect of CN sensitization and N-doping extends the light response to the visible light region; (3) multichannel charges separation and transport among the multijunctions promote the photogenerated carriers separation. These beneficial factors lead to the remarkably higher visible light photocatalytic performance of CN-STO/TN in comparison with the component photocatalysts, 27 times that of TN, 13.5 times that of STO, and 4.9 times that of CN, respectively. These results demonstrate that the combination of morphology tailoring and energy band alignment manipulation is important in designing effective heterojunctions for photocatalytic applications.

An alumina-supported core–shell-structured NiO@PdO catalyst was prepared for lean CH4 combustion. NiO@PdO plays two roles in promoting the reaction. First, the enhanced NiO-PdO interfacial action accelerates the regular tetragonal PdO lattice construction, stabilizes the PdO particles, and suppresses the hydroxyl/water adsorption during the reaction. Second, the dispersion of shell PdO particles over core NiO improves PdO exposure and utilization efficiency. NiO@PdO/Al2O3 with a molar Ni/Pd ratio of 2/1 exhibits a (>)99% CH4 conversion and a good stability at 400 °C with a low 0.2 wt % Pd loading amount, which is among the best of the state-of-the-art Pd-based catalysts with respect to turnover frequency, Pd utilization efficiency, and Ni addition amount. Such interface-promoted core–shell-structured catalyst design strategy is inspiring for improving noble metal utilization efficiency in CH4 oxidation and other related reaction systems.Keywords: catalytic combustion; core−shell; methane; NiO; PdO;

A variety of unique Al(salen) complexes functionalized by imidazolium-based ionic liquid (IL) moieties with the salen ligand at the two sides of 3,3′-position have been successfully prepared, rather than familiar 5,5′-position reported previously. The catalytic activity obtained by these bifunctional catalysts could be superior to those of the binary type catalysts in the formation of five-membered heterocyclic compounds from the cycloaddition reaction of CO2 and three-membered heterocyclic compounds (including terminal epoxides and N-substituted aziridines), presumably due to the distinguished intramolecularly synergistic catalysis, which might lead to perform the cycloaddition reaction at ambient conditions and retain excellent yield and unprecedented chemo- or regioselectivity. Moreover, the polyether-based trifunctional Al(salen) catalysts with the best catalytic performance could be regenerated and reused at least eight times without any obvious decreases in catalytic activity. Finally, the kinetic investigation suggested the structure of catalysts had important influences on the catalytic activity, thereby proposing the possible reaction mechanism.

•Biomimetic oxidation of hydrocarbons in cumene was first reported.•Co-substrate specificity and mechanistic consideration were investigated.•The high-valent MnIV–oxo π-cation radicals were regarded as active species.•The biomimetic process was in accordance with Michaelis-Menten kinetics.Selective aerobic oxidation of hydrocarbons by molecular oxygen to afford valuable oxygen-containing functional compounds is a key challenge in modern chemical industry. Herein, an efficient catalytic system including metalloporphyrins as ideal catalysts and cumene as a co-substrate was developed for the aerobic oxidation of hydrocarbons to afford products with high yields and excellent chemoselectivities. Notably, this biomimetic process was found to be similar to cytochrome P450 monooxygenase-catalyzed reactions according to Michaelis–Menten kinetics. Experimental results and in situ monitoring techniques including the kinetic study, in situ ultraviolet–visible spectroscopy, and in situ electron spin resonance spectroscopy indicated that in situ generated cumyl hydroperoxide acted as an actual oxidant. Its formation was possibly mediated by metalloporphyrins to generate numerous free-radical species, and the high-valent MnIV–oxo π-cation radicals were regarded as active species in the aerobic oxidation. Consequently, both the co-substrate specificity and the possible reaction mechanism were systematically investigated based on the control experiments and results obtained from our previous studies.Download full-size image

•Polyether-based bifunctional Al(salen) oligomers were prepared successfully.•These catalysts presented the enhanced activity in cycloaddition reactions.•The easy-to-handle catalyst could be recyclable and reused by solvent control.•The kinetic investigation reflected the possible reaction mechanism.The solvent-free cycloaddition reaction of carbon dioxide (CO2) with epoxides has been efficiently achieved with the enhanced catalytic activity employing a series of polyether-based salen aluminum oligomers as excellent bifunctional catalysts. These CO2-philic Al(salen) derivatives could act as an easy-to-handle and homogenous catalyst and might present the enhanced recycling performance compared to the polyether-free catalysts. The promising catalysis data such as the reduced apparent activation energy suggested the synergistic effect of the metal center (Lewis acid) and the halide anion (nuclephile) had significant impact on the catalytic performance. Finally, the preliminary kinetic investigations further demonstrated that the reaction was apparent first order with respect to the concentration of epoxide and catalyst and thus followed a possible monometallic synergistic catalytic mechanism, whereas the binary catalytic system was connected with the non-first-order kinetics.Download high-res image (108KB)Download full-size image

•Acetophenone and 1-phenylethanol were separated by biosorption using SMP as adsorbent.•A roll-up effect was observed in continuous adsorption.•SMP can be regenerated with no loss in performance.•Adsorption mechanism was proposed through theoretical calculations and experimental analyses.A polysaccharide-based polymer (abbrev., SMP) was prepared via the crosslinking of starch with 4,4-methylene diphenyl diisocyanate and employed as an adsorbent for selective separation of acetophenone (AP) and 1-phenylethanol (PE) which coexist extensively in petrochemical by-products and effluents. The successful crosslinking was proved by FTIR and XPS, and the rough morphology as well as porous structure was also demonstrated in XRD, SEM and N2 adsorption-desorption analysis. Using SMP as adsorbent, the adsorption kinetics and isotherms were both investigated in single-component system. Both kinetic and thermodynamic parameters of the adsorption process were obtained. Further thermodynamic investigation indicated that the adsorption was exothermic and spontaneous. Compared to the starch-based polymers whose frameworks contain no phenyl ring, SMP exhibits both higher selectivity and capacity for AP in the competitive adsorption. Additionally, increasing the level of crosslinking in SMP favors its adsorption performance. Furthermore, continuous adsorption-desorption indicated high separation ability and regeneration efficiency of SMP. Finally, the mechanism studies suggested that the adsorption mechanisms may be physisorption involving noncovalent interactions, permitting preference to AP over PE.Download high-res image (201KB)Download full-size image

•Pt/TiNT demonstrates superior performance for toluene oxidation.•Pt/TiNT holds rich active sites.•Decomposition of benzoate species is the key step for toluene oxidation.Featuring an assembly of identical pores, TiO2 nanotube array (TiNT) makes an ideal monolith-like support of noble metal catalysts for volatile organic compounds combustion. Herein, the deep oxidation of gaseous toluene over Pt/TiNT and anatase TiO2 (ATiO2) particles supported Pt catalysts are studied and compared. Pt/TiNT demonstrates remarkably enhanced performance over Pt/ATiO2 powder catalyst, and ranges among the best performances of the state of the art Pt based catalysts. A toluene conversion of (>)95% at 185 °C and a multiple heating-cooling cyclic stable performance with a time of (>)300 h are achieved over 0.4 wt% Pt/TiNT. In situ DRIFTS study indicates that toluene is sequentially oxidized to benzaldehyde, benzoate, aliphatic carboxylates species, CO and finally to CO2, and the decomposition of benzoate species is the key step. The unique performance of Pt/TiNT is attributed to its ordered monolith-like structure, well-dispersion and surface enrichment of Pt, and enhanced benzoate species decomposition rate.Download high-res image (85KB)Download full-size image

•Both oxygen vacancy and Pd site can promote the HCHO adsorption over anatase TiO2(101) surface.•The presence of Pd site is beneficial for the formation of oxygen vacancy.•Synergetic effect of oxygen vacancy and Pd site on the interaction between Pd/TiO2(101) and HCHO is demonstrated.Insights into the functions and the synergetic effects of oxygen vacancy and noble metal sites on the performance of the reducible oxide supported noble metal catalysts are very important in designing formaldehyde catalysts. Herein, the roles of oxygen vacancies and Pd sites, and their synergistic effect on the interaction between HCHO and Pd/Anatase TiO2(101) surface were systematically studied by a density functional theory (DFT) study. It is found that both the presence of oxygen vacancy and Pd site can promote the HCHO adsorption over TiO2(101) surface. The presence of Pd site is beneficial for the oxygen vacancy formation by reducing its formation energy. Furthermore, synergetic effect of oxygen vacancy and Pd site on the interaction between Pd/TiO2(101) and HCHO is demonstrated for the case with the co-presence of oxygen vacancy and Pd site. In this situation, the oxygen atom of HCHO molecular occupies the oxygen vacancy and the carbon atom of HCHO connects with the Pd site, and a larger adsorption energy is obtained in comparison with the cases with only oxygen vacancy or Pd site present. These results indicate that both oxygen vacancy manufacturing and Pd doping can strength the HCHO adsorption over TiO2(101) surface, and their synergistic effects further promote the interaction between HCHO and Pd/TiO2 catalyst, which is beneficial for the HCHO oxidation.Download high-res image (276KB)Download full-size image

•Vacancy-rich BiOI were prepared via low concentration nitric acid treatment.•Vacancy-rich BiOI show enhanced photocatalytic activity.•The photocatalytic process is mainly governed by the superoxide and the holes.•Such Vacancy-rich BiOI have a promising practical application in photocatalysis.Searching for simple and effective methods for large-scale production of defective catalysts is of key importance, but remains a big challenge. Herein, we report a simple, scalable and effective method to produce defects in photocatalysts, which is significant for industrial application. Surprisingly, the defects on the photo-thermo-catalysts could not only availably decrease the recombination of photoelectrons and holes, but also increase the production of reactive oxygen species, which demonstrated a superior improvement in photo-thermo-catalytic activity coupled with ultrastable stability. These findings feature the fundamental role of surface defects structure on producing more oxygen reactive species and may create advance avenues for the rational design of extremely efficient photo-thermo-catalysts via surface engineering.Download high-res image (193KB)Download full-size image

•In situ DRIFTS study of O3 adsorption on metal oxides at room temperature.•Using acidic probe molecules (DRIFTS) characterization of surface basicity.•Correlation between basic strength of metal oxides and O3 adsorption.•Study on the competitive adsorption of O3 and CO2.•DRIFTS study of cinnamaldehyde ozonation and benzaldehyde excessive oxidation.In situ DRIFTS were conducted to identify adsorbed ozone and/or adsorbed oxygen species on CaO, ZnO, γ-Al2O3, CuO and α-Fe2O3 surfaces at room temperature. Samples were characterized by means of TG, XRD, N2 adsorption–desorption, pyridine-IR, nitrobenzene-IR, chloroform-IR, and CO2-TPD. Pyridine-DRIFTS measurements evidence two kinds of acid sites in all the samples. Nitrobenzene, chloroform-DRIFTS, and CO2-TPD reveal that there are large amounts of medium-strength base sites on all the metal oxides, and only CaO, ZnO, and γ-Al2O3 have strong base sites. And the benzaldehyde selectivity was increased in the same order of the alkalinity of the metal oxides. With weaker sites, ozone molecules form coordinative complexes bound via the terminal oxygen atom, observed by vibrational frequencies at 2095–2122 and 1026–1054 cm−1. The formation of ozonide O3− at 790 cm−1, atomic oxygen at 1317 cm−1, and superoxide O2− at 1124 cm−1 was detected; these species are believed to be intermediates of O3 decomposition on strong acid/base sites. The adsorption of ozone on metal oxides is a weak adsorption, and other gases, such as CO2, will compete with O3 adsorption. The mechanism of cinnamaldehyde ozonation at room temperature over CaO shows that cinnamaldehyde can not only be oxidized into cinnamic acid, but also be further oxidized into benzaldehyde, benzoic acid, maleic anhydride, and ultimately mineralized to CO2 in the presence of O3.Download high-res image (151KB)Download full-size image

In order to isolate cinnamyl acetate (CAc) and cinnamaldehyde (CA), which coexist in cinnamon oil, a crosslinked polymer of β-cyclodextrin polyurethane (CDPU) was synthesized via a facile route and investigated as a selective adsorbent. The successful crosslinking was confirmed by FTIR, TG-DSC, XRD, SEM and N2 adsorption–desorption analysis. The adsorption mechanism was investigated through a series of instrumental analyses and theoretical calculations, indicating that the combination of non-covalent interactions (e.g., hydrogen bonding, hydrophobic interactions) accounts for the superior affinity of CAc to CDPU, compared with CA. The adsorption behaviors of CAc and CA on CDPU were performed in the static adsorption mode, in which CDPU exhibited a selective adsorption property to CAc. The adsorption kinetics and isotherms in a single component system agreed well with the pseudo-second-order kinetic model and Freundlich isotherm model, respectively. It is noteworthy that the equilibrium adsorption amount was enhanced in the presence of the co-solute, presumably resulting from the cooperative effect arising from Lewis acid–base and π–π stacking interactions between the adsorbed CAc and CA molecules. Due to the stronger adsorption affinity of CAc to CDPU, adsorption enhancement of CAc in the presence of CA is greater than that of CA in the presence of CAc, resulting in higher CAc/CA selectivity with increasing concentrations of the equimolar mixture of CAc and CA. Additionally, CDPU could be easily regenerated and maintained high adsorption capacities and separation efficiency even after six adsorption/desorption cycles.

Herein, we report a photoanode of g-C3N4/WO3 heterojunctions with exceptional ability and stability for photoelectrochemical (PEC) water splitting which achieved a high photocurrent density of 1.92 mA cm−2 at +1.23 V versus (vs.) RHE which is about 2 times higher than that of the pristine WO3 photoanode (0.71 mA cm−2).

Reversible conversion of Cu2+ and Cu+ under illumination and with oxidation is demonstrated over CuxO/SrTiO3. Such Cu2+/Cu+ homeostasis together with its photosensitizer function and p–n heterojunction formation has lead to highly active and stable visible photocatalytic performance. This strategy will provide some new insights into the design of highly efficient photocatalysts.

There are wide interests in developing high-performance electrode materials for electrochemical energy storage and conversion devices. Among them, transition metal nitrides (TMNs) are suitable for a wide range of devices because they have better electrical conductivity than the oxides and excellent catalytic properties. In particular, properly designed nanostructured TMNs offer additional advantages for performance enhancement. However, reviews of the rapid utilization of metal nitrides as electrode materials are still not much. In this mini-review, we present a recent (mostly since 2015) update on nanostructured TMNs as high-performance electrode materials for energy storage devices and water splitting; we discussed how a judicious nanostructure design will lead to improving performance in lithium ion battery, supercapacitor and Li-ion capacitor, as well as in electrochemical water splitting (oxygen and hydrogen evolution reactions). Knowledge about this review on metal nitrides is aimed at sharing a wide view in recent TMNs synthetic development, applications, prospects and challenges.Download high-res image (262KB)Download full-size image

•Nickel hydroxide promoted Pt nanoparticles were prepared.•Hydroxyl groups confined interface promoted HCHO oxidation.•PtNi(OH)x/γ-Al2O3 demonstrated excellent HCHO oxidation performance.Rational design of efficient noble metal catalysts and its application process by the interface promoted strategy is an emerging research field. Herein, highly efficient nickel hydroxide promoted PtNi(OH)x/γ-Al2O3 catalysts for room temperature HCHO oxidation was developed. PtNi(OH)x/γ-Al2O3 demonstrates remarkably better performance than the state of the art non-reductive oxide supported Pt catalysts, and ranges among the best performance of the reductive metal oxide supported Pt catalysts. A (>)99% HCHO conversion and a (>)100 h stable performance at 30 °C were obtained over PtNi(OH)x/γ-Al2O3 with a 0.3 wt% Pt loading amount. Various characterizations, including in situ DRIFTS study, were performed to understand the reason for the enhanced performance of PtNi(OH)x/γ-Al2O3. The superior performance is attributed to the formation of enormous Pt/Ni(OH)x interface, and the preferred hydroxyl facilitated HCHO oxidation pathway through formate oxidation by the abundant associated hydroxyl groups nearby the Pt active sites. Such hydroxyl groups confined interface promotion strategy may bring new insight into the designing of highly efficient bimetallic catalysts and its potential technological applications for HCHO removal.Download high-res image (124KB)Download full-size image

•c-MWCNTs presented excellent activity in aerobic oxidation ketones.•c-MWCNTs showed good recyclability and reusability.•Mechanism of c-MWCNTs to stabilize the radical species in the reaction.Multi-walled carbon nanotubes (MWCNTs) as metal-free catalysts presented excellent activity and selectivity in the Baeyer-Villiger oxidation of ketones to corresponding lactones in the presence of molecular oxygen and benzaldehyde. Different factors including catalyst, solvents, amount of catalyst were systematically investigated. Compared with MWCNTs, carboxylic multi-walled carbon nanotubes (c-MWCNTs) catalyst exhibited higher performance for the oxidation of ketones, showing good recyclability and reusability. The yield of ε-caprolactone was obtained with 94% under the optimum conditions. Also, c-MWCNTs presented excellent activity towards the oxidation of various cyclic ketones to the corresponding lactones. The introduced carboxyl group on the surface of MWCNTs was favorable to obtain high dispersion in the reaction solution. In addition, the recording of in situ Electron Paramagnetic Resonance (EPR) and Raman spectroscopy indicated that carboxyl group could significantly stabilize the radical species in the reaction.Download full-size imageThe carboxylic multi-walled carbon nanotubes (c-MWCNTs) can act as metal-free catalyst to against the inhibition, which are in favor of the chain propagation reactions to assure of producing peroxybenzoic acid to the oxidation of cyclohexanone.

Tannic acid (TA)/KI as a cheap, green, highly-efficient, biocompatible, and recyclable catalytic system represents the excellent synergistic effect in the cycloaddition reactions of CO2 and epoxides under solvent-free conditions, which is originated from hydrogen bonding between the hydrogen atoms of phenolic hydroxyl groups within TA and the oxygen atom of the epoxide. Therefore, it is considerable to be a sustainable methodology for the utilization of bio-resources.

AbstractCytochrome P450 enzyme-copper phosphate hybrid materials with flower-like shape were prepared with a simple but efficient coprecipitation method. The growth process of the hybrid flowers can be divided into three successive steps: coordination/nucleation, growth, and further ripen. The concentration of enzymes in the mother liquor exerted great influence on the morphology and surface enzyme content of the nano-composites. The catalytic performance in the reaction of selective oxidation of sulfide to sulfoxide was also investigated. The hybrid flowers exhibited superior catalytic performance: satisfied thioanisole conversion and selectivity to methyl phenyl sulfoxide (both above 97%) with H2O2 as oxidant under mild reaction conditions, excellent stability and recyclability, and wide scope of substrates. Such results indicate that the hybrid materials are potentially good candidates in the industrial enzyme catalysis.

Water splitting into hydrogen and oxygen in order to store light or electric energy requires efficient electrocatalysts for practical application. Cost-effectiveness, abundance, and efficiency are the major challenges of the electrocatalysts. Herein, this paper reports the use of low-cost 304-type stainless steel mesh as suitable electrocatalysts for splitting of water. The commercial and self-support stainless steel mesh is subjected to exfoliation and heteroatom doping processes. The modified stainless steel electrocatalyst displays higher oxygen evolution reaction property than the commercial IrO2, and comparable hydrogen evolution reaction property with that of Pt. More importantly, an all-stainless-steel-based alkaline electrolyzer (denoted as NESSP//NESS) is designed for the first time, which possesses outstanding stability along with lower overall voltage than the conventional Pt//IrO2 electrolyzer at increasing current densities. The remarkable electrocatalytic properties of the stainless steel electrode can be attributed to the unique exfoliated-surface morphology, heteroatom doping, and synergistic effect from the uniform distribution of the interconnected elemental compositions. This work creates prospects to the utilization of low-cost, highly active, and ultradurable electrocatalysts for electrochemical energy conversion.

•CO2 was photocatalytic reduction to formic acid by Cu/BiYO3 under visible-light.•The oxygen vacancies were formed in Cu/BiYO3.•The separation of photo-generated carriers of BiYO3 was improved by doping with Cu.•The Cu/BiYO3 has a better electronic transmission capacity than the BiYO3.•The photocatalytic activity of BiYO3 was enhanced by doping with Cu.Bismuth yttrium oxide (BiYO3) photocatalysts doped with different Cu amounts were synthesized via a hydrothermal method, characterized and applied for the photocatalytic reduced CO2 to formic acid under the visible light irradiation. The particle size of Cu/BiYO3 was smaller than that of BiYO3, and the surface area of BiYO3 was increased from 6.75 m2/g to 18.64 m2/g when the Cu doping amount of was 2.0%. The FT-Raman results reveal the formation of oxygen vacancies after doping with Cu, which suppressed the charge recombination, and the electrochemical impedance spectroscopy (EIS) proved that the Cu/BiYO3 has a better electronic transmission capacity. The HCOOH amount of photocatalytic reduction of CO2 was 2.04 μmol /mL by using 2.0% Cu/BiYO3 as photocatalyst, which was 2.2 times than that of BiYO3. The highly improved performance of the 2.0% Cu/BiYO3 can be ascribed to the increased surface area, increased light absorption, and efficient charge separation.Download high-res image (125KB)Download full-size image

AbstractA simple cooperative catalytic system was successfully developed for the solvent-free N-formylation of amines with CO2 and hydrosilanes under ambient conditions, which was composed of a Zn(salen) catalyst and quaternary ammonium salt. These commercially available binary components activated the Si−H bonds effectively, owing to the intermolecular synergistic effect between Lewis base and transition metal center (LB–TM), and subsequently facilitated the insertion of CO2 to form the active silyl formats, thereby leading to excellent catalytic performance at a low catalyst loading. Furthermore, the bifunctional Zn(salen) complexes, with two imidazolium-based ionic-liquid (IL) units at the 3,3′-position of salen ligand, acted as intramolecularly cooperative catalysts, and the solvent-regulated separation resulted in facile catalyst recycling and reuse.

Cost-effective catalysts for volatile organic compound (VOC) oxidation are critical to energy conversion and environmental protection. Herein, we developed new, low-cost and high-performance alkali-promoted 3D-NiCo2O4 nanosheet catalysts for HCHO oxidation at room temperature. Benefiting from the large surface area, high adsorption capacity and surface hydroxyls, the alkali-promoted 3D-NiCo2O4 nanosheet catalysts show substantially high catalytic activities for HCHO oxidation. The alkali-promoted 3D-NiCo2O4 nanosheets yield a remarkable HCHO conversion efficiency of 95.3% at room temperature, which is not achieved by any non-precious metal based catalysts at such low temperature. Additionally, the as-prepared alkali-promoted 3D-NiCo2O4 nanosheets retained excellent catalytic performance after 200 h, which can be applied to practical applications. This work provides a feasible approach to improve the efficiency of metal oxides for HCHO oxidation at low temperature.

Defect engineering is regarded as one of the most active projects to monitor the chemical and physical properties of materials, which is expected to increase the photocatalytic activities of the materials. Herein, oxygen vacancies and IO3– doping are introduced into BiOI nanosheets via adding NaH2PO2, which can impact the charge carrier dynamics of BiOI photocatalysts, such as its excitation, separation, trap, and transfer. These oxygen-deficient BiOI nanosheets display attractive photocatalytic activities of gaseous formaldehyde degradation and methyl orange under visible light irradiation, which are 5 and 3.5 times higher than the BiOI samples, respectively. Moreover, the comodified BiOI also displayed superior cycling stability and can be used for practical application. This work not only develops an effective strategy for fabricating oxygen vacancies but also offers deep insight into the impact of surface defects in enhancing photocatalysis.Keywords: bismuth oxyhalide; charge transport; IO3− doping; oxygen vacancy; photocatalysis

Herein, we demonstrate a simple strategy to boost the photocatalytic performance of BiOI by introducing oxygen defects into the BiOI. The oxygen-deficient BiOI exhibits superior photocatalytic performance for the degradation of formaldehyde gas. The enhancement of photocatalytic activity is due to the enhanced separation and migration efficiency of photogenerated electrons and holes.

•A β-CD modified poly(butyl methacrylate) resin (poly(BMA-Co-CD) was synthesized.•The resin has a low BET surface area and an effectively nonporous structure.•Excellent adsorption properties toward BETX from aqueous solutions were investigated.Efficient removal of benzene, toluene, ethylbenzene and xylene (BTEX) from aqueous solution has been studied with a β-cyclodextrin (β-CD) modified poly(butyl methacrylate) resin (poly(BMA-Co-CD). The effects of the amount of β-CD in poly(BMA-Co-CD), pH, ionic strength, contact time, and temperature of the solution on the adsorption of BTEX were investigated in details. Adsorption data were fitted very well to Freundlich model. The results showed that the β-CD groups on the resin played a significant role for adsorption of BTEX, and quantum chemical calculation confirmed the experimental results. The resin exhibits good performance e.g. high adsorption capacity, high separation efficiency, and easy regeneration.A β-CD modified poly(butyl methacrylate) resin was synthesized and employed as an effective sorbent for the removal of benzene, toluene, ethylbenzene and xylene (BTEX) from aqueous solutions.

Perovskite structured SrTiO3 (STO) was synthesized by a hydrothermal method followed by a second hydrothermal treatment with H2O or NaOH (STO-H2O or STO-NaOH) for the photocatalytic mineralization of gaseous toluene. The second hydrothermal treatment enhances the light absorption and enriches the surface hydroxyl groups of STO. The surface hydroxyls’ enrichment of STO promotes the generation of hydroxyl radicals and the separation of photocarriers by the combination of hydroxyl with holes, induces a negative shift of its band edge, and benefits the reduction of adsorbed oxygen. The facile generation of reactive radical species, enhanced light absorption, and improved photocarrier separation together lead to greatly enhanced photocatalytic efficiency of STO-NaOH. Toluene was completely oxidized into CO2 under ultraviolet light illumination for 6 h at room temperature, demonstrating better performance than STO and commercial P25 catalysts. Such a surface hydroxylation promotion strategy may lead to new perceptions of designing an efficient photocatalyst.

β-cyclodextrin grafted on lignin (l-β-CD) was prepared by the reaction of β-cyclodextrin (β-CD) and lignin with epichlorohydrin (EPI) as a cross-linking agent. The polymer was characterized by Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Scanning electron microscopy (SEM), and solid-state nuclear magnetic resonance spectroscopy (CP-MAS-NMR). It was used as an inverse phase transfer catalyst for selective oxidation of benzyl alcohol (BzOH) to benzaldehyde (BzH) with hydrogen peroxide as the oxidant. The effects of various reaction variables, e.g., catalyst, the amount of catalyst, stirring speed, reaction temperature, oxidant, and cocatalyst on the catalytic performances were investigated. Under optimal conditions, high selectivity (>99%) was observed for the oxidation of BzOH under rather mild conditions. A plausible mechanism for the liquid-solid phase oxidation of BzOH has been proposed. Synergistic effects based on weak interactions between catalyst and support played an important role for the effective oxidation of BzOH under solution condition. The catalyst can be easily recycled and reused without a significant loss in reaction activity and selectivity, which would lead to its potential application foreground for environmental friendly synthesis of BzH.β-cyclodextrin grafted on lignin (l-β-CD) has been used as a metal-free catalyst for selective oxidation of benzyl alcohol to benzaldehyde and excellent catalytic performances based on synergistic effects of hydrogen bonding between catalyst and support were achieved.

Fossil fuels are currently the major energy source and are rapidly consumed to supply the increasing energy demands of mankind. CO2, a product of fossil fuel combustion, leads to climate change and will have a serious impact on our environment. There is an increasing need to mitigate CO2 emissions using carbon–neutral energy sources. Therefore, research activities are devoted to CO2 capture, storage and utilization. For instance, photocatalytic reduction of CO2 into hydrocarbon fuels is a promising avenue to recycle carbon dioxide. Here we review the present status of the emission and utilization of CO2. Then we review the photocatalytic conversion of CO2 by TiO2, modified TiO2 and non-titanium metal oxides. Finally, the challenges and prospects for further development of CO2 photocatalytic reduction are presented.

We developed a low-cost and high-performance TiO2/CeO2 nanowire-based catalyst for efficient catalytic volatile organic compound oxidation at low temperature. The TiO2/CeO2 nanowires yield a remarkable HCHO conversion efficiency of 60.2% at a low temperature of 60 °C and have excellent catalytic stability as well as good activity for toluene oxidation.

•A blend of PA-6 and PS-DVB has been prepared.•Excellent adsorption properties was observed.•The difference of the interactions is main mechanisms to separate curcumin, DMC, BDMC from the turmeric, respectively.In this study, a blend of polyamide-6 and poly(styrene–divinyl benzene) (PA–PS–DVB) was prepared and used to produce high-purity individual curcuminoids such as curcumin, demethoxycurcumin (DMC), and bisdemethoxycurcum (BDMC) from turmeric crude extracts. The effects of pH and temperature on the adsorption capacities of the curcuminoids were investigated in details. Dynamic experiments on packed columns of PA–PS–DVB resin were performed, and an optimized process for gradient elution was obtained and the obtained products were further recrystallized in isopropanol. The purities of curcumin, DMC, and BDMC increased up to 99.28%, 98.8%, and 98.2%, respectively. In conclusion, the results in this work provide a cost-effective method for large-scale production of high-purity individual curcuminoids.Functionalization of polyamide-6 into poly(styrene–divinyl benzene) adsorption resin has been applied to separate the curcuminoids and excellent adsorption properties based on synergistic effects of hydrogen bonding and π–π conjugation were achieved. The differences of the interactions were main mechanisms to elute curcumin, DMC, and DBMC from the resin with concentration gradient of ethanol.

Generally, gaseous propylene is hard to oxidize directly in liquid phase by dioxygen under mild conditions. Here, the liquid phase epoxidation of propylene to propylene oxide (PO) using molecular oxygen catalyzed by manganese porphyrins (MnTPPCl) in the presence of benzaldehyde was developed. Manganese(III) porphyrin exhibited excellent activity for the selective oxidation of propylene under mild conditions. The conversion of propylene and selectivity towards PO can reach 38% and 80%, respectively. The turnover frequency (TOF) of MnTPPCl catalyst reached 1840 h−1. Experiment evidences that the generation of peroxide and Mn(IV) oxo species during propylene epoxidation occurred, which was confirmed by in situ IR, in situ UV and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). On the basis of the experimental results, the mechanism for the epoxidation of propylene in the presence of metalloporphyrins and benzaldehyde with dioxygen was proposed. The mechanism is also supported by density functional theory (DFT) calculations.

Highly ordered pore-through TiO2 nanotube arrays (TiNT) prepared by an electrochemical anodization method were modified with MnO2 and used as the support for a Pt/MnO2/TiNT catalyst. The monolith-like Pt/MnO2/TiNT was then applied to low-concentration HCHO oxidation with enhanced efficiency. The effect of the MnO2 promotion on its performance for HCHO oxidation was studied with respect to the behavior of adsorbed species on the catalyst surface using in situ diffuse reflectance Fourier transform spectroscopy. In comparison with Pt/TiNT, Pt/MnO2/TiNT shows higher activity under parallel preparation and test conditions. A HCHO conversion of 95% with a more than 100 h stable performance is achieved over Pt/MnO2/TiNT at 30 °C with a low 0.20 wt % Pt loading amount. The superior performance is related to the specific monolith-like structure and its confinement effect, metal–support interaction, and superior HCHO adsorption and storage properties of Pt/MnO2/TiNT.

Degrading and removing harmful compounds by the use of semiconductor photocatalysts has been testified to be and effective and attractive green technique in wastewater treatment. Herein, carbon dots sensitized BiOI with highly exposed {001} facets has been prepared and used to study the photocatalytic degradation of methyl orange (MO). Due to the improved charge separation, transfer, and optical absorption, the photocatalytic performance for methyl orange degradation of the carbon dots/{001} BiOI nanosheets is 4 times higher than that of the {001} BiOI nanosheets under visible light irradiation. Additionally, the carbon dots/{001} BiOI nanosheets also have superior stability after 5 cyclings.

Hydrogen, a clean energy carrier with high energy capacity, is a very promising candidate as a primary energy source for the future. Photoelectrochemical (PEC) hydrogen production from renewable biomass derivatives and water is one of the most promising approaches to producing green chemical fuel. Compared to water splitting, hydrogen production from renewable biomass derivatives and water through a PEC process is more efficient from the viewpoint of thermodynamics. Additionally, the carbon dioxide formed can be re-transformed into carbohydrates via photosynthesis in plants. In this review, we focus on the development of photoanodes and systems for PEC hydrogen production from water and renewable biomass derivatives, such as methanol, ethanol, glycerol and sugars. We also discuss the future challenges and opportunities for the design of the state-of-the-art photoanodes and PEC systems for hydrogen production from biomass derivatives and water.

A series of monometallic salen aluminum complexes were prepared by covalent linkage of the imidazolium-based ionic liquid moieties containing various polyether chains with the salen ligand at the two sides of the 5,5′-position. The salen aluminum complexes proved to be efficient and recyclable homogeneous catalysts towards the organic solvent-free synthesis of cyclic carbonates from epoxides and CO2 in the absence of a co-catalyst. The catalysts presented excellent “CO2 capture” capability due to the molecules containing polyether chains and the metal aluminum center, in which >90% yield of cyclic carbonate could be obtained under mild conditions. The catalysts can be easily recovered and six times reused without significant loss of activity and selectivity. Moreover, based on experimental and previous work, the “CO2 capture and activation” cycloaddition reaction mechanisms by monometallic or bimetallic salen aluminum complexes were both proposed.

A series of novel zinc complexes were prepared by covalent linkage of various imidazolium-based ionic liquid moieties with the 2,2′-bipyridine ligand on the two sides of the 4,4′-position. The zinc(II) complexes containing the rigid N-chelating ligand proved to be stable, highly efficient and easy-to-handle catalysts towards the synthesis of cyclic carbonate from epoxide and CO2 without the use of any co-catalyst or organic solvent. The catalysts can be easily recovered and reused without significant loss of activity and selectivity by control of the solvent. The kinetic study uncovered that the reaction was first-order with respect to the epoxide. Moreover, a plausible reaction mechanism was proposed, in which the zinc center could promote ring-opening of the epoxide for the synergetic effect with the anion X− in ILs.

With the increasingly serious environmental problems, photocatalysis has recently attracted a great deal of attention, with particular focus on water and air purification and disinfection. Herein, we show an electroreduction strategy to improve significantly the solar absorption and donor density of BiOI nanosheet photocatalyst by introducing oxygen vacancies. These oxygen-deficient BiOI nanosheets exhibit an unexpected red shift of about 100 nm in light absorption band and 1 order of magnitude improvement in donor density compared to the untreated BiOI nanosheets and show 10 times higher photocatalytic activity than the untreated BiOI nanosheets for methyl orange (MO) degradation under visible light irradiation. Moreover, the as-prepared oxygen-deficient BiOI nanosheets also have excellent cycling stability and superior photocatalytic performance toward other dye pollutants.Keywords: bismuth oxyhalide; oxygen vacancy; photocatalytic; visible light

Strong metal-support interaction (SMSI) in titania supported noble metals has been a subject of many studies due to its importance to many fields of science, in particular to material science and catalysis system. H2 reduction at a high temperature has been commonly considered as the inducement to SMSI in TiO2 supported noble metals. This work, however, demonstrates that SMSI in Pt/TiO2 can occur through mild NaBH4 and HCHO solution reduction processes based on CO chemisorption, transmission electron microscopy, and X-ray photoelectron spectroscopy characterizations. Moreover, the effect of TiO2 crystalline forms on the degree of SMSI in NaBH4 reduced Pt/TiO2 and the performance of the as-reduced catalysts for trace toluene combustion reaction were studied. It was found that the degree of SMSI in Pt/TiO2 drew a significant effect on the catalytic performance. Our discovery provides a new way to control the interaction between noble metals and the TiO2 support as well as their catalytic activities.

Highly ordered pore-through TiO2 nanotube arrays (TiNT) were prepared by an electrochemical anodization method and used as the support for a Pt/TiNT catalyst. The Pt/TiNT was then applied to the trace HCHO oxidation. The effect of Pt/TiO2 structural properties on its performance was studied with respect to the behavior of adsorbed species on the catalyst surface using in situ DRIFTS. In comparison with the commercial TiO2 powders (P25 and anatase) supported Pt catalysts, Pt/TiNT shows higher activity under parallel preparation and test conditions. A HCHO conversion of 95% with a more than 100 h stable performance is achieved over Pt/TiNT at 30 °C with a low 0.4 wt % Pt loading amount. The superior performance is related to the specific monolith-like structure, confinement effect and metal–support interaction in Pt/TiNT. Finally, the reaction mechanism is presented based on the in situ DRIFTS study and XPS characterization to explain the performance difference among the Pt/TiO2 samples with different morphologies.

2-Hydroxypropyl-β-cyclodextrin was immobilized onto cellulose with epichlorohydrin as a cross-linker. The obtained polymer, as biomimetic catalyst, was used to mediate synthesis of benzaldehyde in aqueous solution. The functionalized mimetic enzyme played a crucial role on catalytic oxidation of cinnamaldehyde with remarkable substrate conversion and product selectivity. Synergistic effect based on weak interactions between the polymer and the substrate results in significant promotion of the catalytic performance. The catalyst could be recycled without apparent loss of the original activity.Keywords: 2-Hydroxypropyl-β-cyclodextrin polymer; Benzaldehyde; Mimetic enzyme; Substrate specificity; Synergistic effect

Porous anodized aluminum oxide (AAO) structure consists of an assembly of identical pores having nanometer dimensions that span a flow reactor so as to produce an array of nano reactors, named as a catalytic nanolith. In order to understand the applicability of the nanolith in volatile organic compounds (VOCs) catalytic combustion and correlate the catalytic performance of the nanolith with its structure, a theoretical analysis of an AAO nanolith reactor dispersed with Pt for the catalytic combustion of selected VOCs (a mixture of naphthalene, propylene, propane and methane) is reported. A one-dimensional adiabatic reactor model has been developed, in which a mixed flow model considering the effect of component diffusion inside the nanopores was adopted, and the pressure drop across the nanolith nanopores as well as the exothermic nature of VOCs combustion were considered. The influence of the operational and design parameters, such as inlet temperature, pressure, and the balance gas as well as the Pt loading density, pore size and wall thickness, on the nanolith performance were studied. The results show that the pressure drop and component diffusion contributions play important roles in the performance of the nanolith reactor. These two factors also relate to the nanolith reactor design parameters, such as pore size, wall thickness and Pt dispersion etc. Considering that all these parameters plus its reactivity can all be readily tailored, the AAO nanolith reactor offers the potential for applications in VOCs catalytic combustion.

The CuO–Fe2O3–ZrO2/HZSM-5 bifunctional catalyst was prepared and used for the direct synthesis of dimethyl ether (DME) from CO2 and H2. The results revealed that doping the CuO–Fe2O3 catalyst with ZrO2 might increase the specific surface area and change the chemical combination state of CuO by decreasing the outer-shell electron density of Cu via an obvious change in the interaction between CuO and Fe2O3. Addition of ZrO2 to the catalyst strongly affects the hydrocarbon selectivity. When using the CuO–Fe2O3–ZrO2/HZSM-5 bifunctional catalyst system, both the conversion of CO2 and the yield of DME were much higher than those obtained using CuO–Fe2O3/HZSM-5 as catalysts. Reactions carried out at 260 °C and 3.0 MPa with a gaseous hourly space velocity of 1500 mL·gcat–1·h–1 using CuO–Fe2O3–ZrO2/HZSM-5 with 1.0 wt % ZrO2 as the hydrogenation catalyst provided a 28.4% conversion of CO2 with 64.5% selectivity for DME.

This work examines the H2 production from methanol (MeOH)–formic acid (FA)–steam (H2O) system (FSRM) by thermodynamic analysis using the Gibbs free energy minimization method. The compounds considered in FSRM are CH3OH, HCOOH, H2O, CO2, CO, H2, HCOOCH3, HCHO, and CH3OCH3 and together with or without CH4 and C (graphite). The addition of FA lowers the enthalpy of the system and favors the heat recycle. Thermal-neutral (TN) conditions are obtained, at which the heat released from exothermic reactions makes up exactly for the requirement of the endothermic reactions. For the case with consideration of CH4 and C formation, C and CH4 formation is thermodynamically dominated at a low temperature (<400 °C). High temperature is favorable for H2 production and can effectively inhibit CH4 and carbon formation, but it also leads to high CO yield. High H2O/MeOH ratio can effectively suppress CO, CH4, and C formation and improve H2 mole fraction at 200, 400, and 600 °C. Although the increase in FA/MeOH ratio leads to low equilibrium H2 mole fraction and high CO concentration, TN conditions can be realized for wide range of H2O/MeOH and FA/MeOH ratios. For the case without consideration of CH4 and C formation, which are only applicable to situations in which byproducts C and CH4 formation are limited, the thermodynamic data may be more agreeable with the reported experimental results. Under TN conditions, the H2 mole fraction can be around 0.51 with a CO mole fraction as low as ∼0.001 for H2O/MeOH = 2 and FA/MeOH = 5 or 6.

A convenient and selective oxidation of alcohols with aqueous hydrogen peroxide to give the corresponding carbonyl compounds under solvent-free conditions has been developed. By applying ruthenium-bis(benzimidazole)pyridinedicarboxylate complex [Ru(bbp)(pydic)] as catalyst, primary, and secondary alcohols were oxidized to aldehydes and ketones in good yield and excellent selectivity under mild conditions.The ruthenium complex-catalyzed oxidation of primary and secondary alcohols to carbonyl compounds using hydrogen peroxide as oxidant under solvent free conditions has been developed.Figure optionsDownload full-size imageDownload as PowerPoint slide

Anatase and rutile have the same chemical composition as TiO2 but different crystalline structures and surface structures, which draws effect on the properties of their supported catalysts. Additionally, titania mixture, e.g., Degussa P25, which consists of both anatase and rutile, presents different physicochemical properties with anatase and rutile. In this work, P25-, anatase- or rutile-supported copper oxide catalysts (signed as CuO/P25, CuO/A and CuO/R) were prepared and characterized to study the titania support effect on the physicochemical properties and catalytic properties for the trace CH4 combustion. It is found that the activity of CuO/R is better than the corresponding CuO/A sample when their pore size and specific surface area are comparable, which is attributed to the different chemical states of the copper oxide caused by the different TiO2 support polymorphs. The loading of CuO and subsequent calcination promotes more significant sintering and anatase to rutile transform for CuO/P25 than those for CuO/A. Thus, CuO/R shows better stability than CuO/P25.Graphical abstractHighlights► More significant anatase to rutile transform happens for CuO/P25 than those for CuO/anatase. ► TiO2 polymorphs affect both the activity and stability of CuO/TiO2 catalysts. ► CuO/rutile shows higher activity than CuO/anatase. ► CuO/rutile shows better stability than the mixed phase TiO2 supported CuO catalyst.

Highly efficient procedure for preparing imines from the oxidative coupling of amines catalyzed by metalloporphyrins using water as the only solvent has been developed. Manganese porphyrin showed an excellent activity for the oxidative coupling of a wide range of amines under mild conditions. Further investigations of the oxidative coupling reaction led to the elucidation of the possible mechanism.

Two proline derivatives, (S)-2-aminomethylpyrrolidine and (R)-2-aminomethylpyrrolidine modified β-CD (CD-1, CD-2) were synthesized in the yields of 31% and 14%. Their self-inclusion conformations were characterized by 1H ROESY NMR studies and quantum calculation. When CD-1 was applied to asymmetric aldol reactions, up to 94% ee was obtained. Substrate selectivity was also observed in these asymmetric aldol reactions.

Inspired by β-CD, a macrocyclic oligomers of d-(+)-glucopyranose and a renewable material, which could be obtained from starch, that can promote a lot of organic reactions in water, a green solvent, several amino alcohol-modified β-CDs CD-1 to CD-7 were synthesized in the yields of 36–61%. Their conformations in vacuum and in aqueous solution were optimized by quantum calculation. Their complexes with sodium molybdate prepared in situ were characterized by 1H NMR and were applied in the asymmetric oxidation of thioanisole. Their performance in inducing enantioselectivity was investigated in detail. For the optimal one, CD-1, moderate enantioselectivity (56% ee) was achieved in aqueous CH3COONa–HCl buffer solution (pH 7.0). The abilities of CD-1 to CD-7 to induce asymmetry are highly dependent on the pH value of the reaction medium and the structure of the modifying group. The origin of the moderate enantioselectivity and the reaction mechanism were investigated with the aid of 1H ROESY NMR studies and quantum calculation. The moderate enantioselectivity was attributed to the two different binding models between CD-1 and thioanisole, which could be defined as intramolecular catalysis and intermolecular catalysis, in which intramolecular catalysis gave (S)-methyl phenyl sulfoxide and intermolecular catalysis gave (R,S)-methyl phenyl sulfoxide.Graphical abstractTwo different binding models between CD-1 and thioanisole resulted in two different catalytic oxidation models, intramolecular and intermolecular catalysis, gave the moderate enantioselectivity, and was consistent with quantum calculation.Highlights► Seven amino alcohol-modified β-CDs were synthesized. ► Amino alcohol-modified β-CDs induced the asymmetric oxidation of thioanisole. ► The pH value of medium and the modifying group determined the enantioselectivity. ► Quantum calculation was employed to probe the reaction mechanism. ► Quantum calculation was in good consistency with the experimental results.

A novel selective separation method for cinnamaldehyde and benzaldehyde has been developed using insoluble β-cyclodextrin polymer as a host and cinnamaldehyde and benzaldehyde as model guests. The insoluble β-cyclodextrin polymer could form inclusion complex with cinnamaldehyde and benzaldehyde in solid state, so as to selectively separate benzaldehyde and cinnamaldehyde. The inclusion equilibrium constants for cinnamaldehyde and benzaldehyde over the β-cyclodextrin polymer have been calculated through their solid UV–vis spectra, and the binding energies between β-cyclodextrin polymer and the two substrates complexes have been calculated with ONIOM2(B3LYP/6-31G(d):PM3) and semi-continuum solvation model. The driving force of the separation between cinnamaldehyde and benzaldehyde is through the different weak interaction with β-cyclodextrin polymer, i.e., hydrogen bond interaction, which is evidenced by the different binding energies and different inclusion equilibrium constants.Graphical abstractSelective separation attained by the structures with different binding energies for the β-CDP guest complexes.Highlights► Novel selective method was used to separate cinnamaldehyde and benzaldehyde using insoluble β-cyclodextrin polymer. ► The difference of binding energies obtained by ONIOM is an important characteristic for separation of the mixtures. ► Separation factor k is why we could selectively separate cinnamaldehyde from benzaldehyde.

A new high temperature tube–shell membrane reactor (MR) design for separation and utilization of CO2 from the flue gas and for simultaneous production of syngas through carbon dioxide reforming of methane (CRM) is reported. The MR is based on a dual-phase CO2 permeation membrane consisting of mixed-conducting oxide and molten carbonate phases. High temperature CO2-containing flue gas and CH4 are respectively fed into the shell and tube sides of the reactor packed with a reforming catalyst. Under performance conditions, CO2 permeates selectively through the membrane from the shell side to the tube side and reacts with CH4 to produce syngas. Additionally, the heat from the flue gas can transfer directly through the membrane to provide energy for the endothermic CRM reaction. An isothermal steady-state model was developed to simulate and analyze CRM in the MR in this work. The effect of the design and operational parameters, such as inlet CH4 flow rate, shell side CO2 partial pressure and the flue gas composition, i.e., containing O2 or not, as well as the membrane thickness on the reactor performance with respect to the CH4 conversion and the CO2 permeation flux were investigated and discussed. The results show that the MR has a high efficiency in separating and utilizing CO2 from the flue gas. For a CH4 space velocity of 3265.31 h−1, with a membrane thickness of 0.075 mm and the shell side CO2 partial pressure of 1 atm, a CH4 conversion of 48.06% and an average CO2 permeation flux of 1.52 mL(STP) cm−2 min−1 through the membrane tube at 800 °C are obtained. Further improvement of the MR performance can be achieved by involving O2 in the permeation process.

The inclusion processes of α,β-cyclodextrins (α,β-CDs) with 2-phenyl-1,3-dioxolane (d), its dihydrate (e) and tetrahydrate (f) have been investigated using PM3, B3LYP and ONIOM2 methods. Solvent effects on the inclusion processes have been corrected using Onsager continuum solvation model combining with B3LYP/6-31G(d). The calculated results indicated that the inclusion complex of head down had an obvious energy advantage over the corresponding head up, and the continuum solvent effect disfavored the formation of inclusion complexes in water. The stability difference between (f)/α-CD head down (−2.90 kcal mol−1) and (f)/β-CD head down (−21.36 kcal mol−1) was closely relative to the yield and the selectivity of the studied deprotection reaction. The deprotection reaction of (d) in water might proceed in a three-step mechanism as follows. Firstly, (d) integrated with four H2O molecules to form the tetrahydrate (f). Then, (f) entered the hydrophobic cavity of α,β-CDs from secondary hydroxyl rim (S–OH) to yield the complexes of (f)/α,β-CDs head down with different stabilities. Finally, the more stable (f)/β-CD head down were transformed into benzaldehyde, H2O and β-CD.

Highly efficient controllable oxidation of alcohols to aldehydes or acids by sodium periodate in the presence of water-soluble manganese porphyrins (meso-tetrakis(N-ethylpyridinium-4-yl)manganese porphyrin, MnTEPyP) with different reaction media has been reported. The manganese porphyrin showed excellent activity for the controllable oxidation of various alcohols under mild conditions. Moreover, different factors influencing alcohol oxidation, for example, oxidant, catalyst amount, temperature, and solvent, have been investigated. A plausible mechanism for the controllable oxidation of alcohol has been proposed.A highly efficient, reaction medium-controlled oxidation of alcohols to acids or aldehydes has been developed in the presence of water-soluble manganese porphyrin and sodium periodate.

Highly efficient oxidation of oximes to carbonyl compounds by molecular oxygen with benzaldehyde as an oxygen acceptor in the presence of metalloporphyrins has been reported. The simple structural manganese porphyrin showed an excellent activity for the oxidative deoximation reactions of various oximes. Moreover, different factors influencing oximes oxidation, that is, catalyst, solvent, and temperature, have been investigated. A possible mechanism for the deoximation reaction has been proposed.The oxidation of oximes to carbonyl compounds proceeds in good yield catalyzed by manganese porphyrin in the presence of molecular oxygen and benzaldehyde.

Polyurea-entrapped palladium nanoclusters have been prepared by interfacial polymerization in W/O emulsion and showed high thermal stability and chemical stability with the content of 0.12 mmol g−1 Pd. This catalyst exhibited dual catalytic activity for reduction of nitro compounds and hydrodehalogenation of aromatic chlorides in atmospheric hydrogen with 100% yield for reduction of nitro compounds and >99% yield for hydrodehalogenation of aromatic chlorides. This immobilizing method was particularly effective and eliminated the need of special chelating groups.

A facile, efficient and substrate-selective oxidation of aldehydes to carboxylic acids with NaClO catalyzed by β-cyclodextrin in water has been developed. A series of aldehydes which could form inclusion complex with β-cyclodextrin (β-CD) were oxidized selectively with excellent yields.

A facile, efficient and substrate-selective oxidation of the primary amines with NaClO as oxidant catalyzed by β-cyclodextrin (β-CD) has been developed in water for the first time, and the behavior of β-cyclodextrin that catalyzed the primary amines to nitriles in water was investigated. It was found that the primary amines which could form host-guest complexes with β-cyclodextrin were oxidized to nitriles with excellent yields at ambient temperature. The results show that β-cyclodextrin worked not only as a solubilizing agent but also as a catalyst in these reactions.

•Ni/bentonite catalysts were prepared by impregnation method.•Aniline was synthesized by gas phase hydrogenation process through nitrobenzene.•Ni/bentonite-20 exhibited higher nitrobenzene conversion and aniline selectivity than other catalysts.•Bentonite was a potential support for nitrobenzene hydrogenation.•Ni/bentonite-20 was stable than Ni/Al2O3 in a 10-hours reaction process.Ni supported on bentonite was prepared by the impregnation method with different nickel contents, applied to the hydrogenation of nitrobenzene to aniline in a fixed-bed reactor, and it was characterized by X-ray diffraction (XRD), H2-temperature programmed reduction (H2-TPR), and X-ray photoelectron spectrometry (XPS). The results showed that Ni/bentonite catalyst with 20 wt% nickel content provided a higher conversion of nitrobenzene and selectivity of aniline compared to other catalysts. NiO was the precursor of the active component of the catalyst, and the small crystallite size as well as the highly dispersed NiO on the Ni/bentonite-20 catalyst, contributed to the catalytic performance. The hydrogenation of nitrobenzene was carried out at 300 °C with a H2 gaseous hourly space velocity of 4800 ml·(g cat)− 1·h− 1 and a nitrobenzene liquid hourly space velocity of 4.8 ml·(g cat)− 1·h− 1 over Ni/bentonite-20. A 95.7% nitrobenzene conversion and 98.8% aniline selectivity were obtained. While the nitrobenzene liquid hourly space velocity was 4.8 ml·(g cat)− 1·h− 1, the yield of aniline was more than 95.0% during a 10-hour reaction.The catalytic reaction was carried out in a fixed bed reactor using Ni/bentonite as catalyst. Aniline was synthesized over metallic Ni with the mixing gases of H2/nitrobenzene. Bentonite acted as the support in this nitrobenzene hydrogenation process. Reaction carried out at 300 °C with a H2 gaseous hourly space velocity of 4800 ml·(g cat)− 1·h− 1 and a nitrobenzene liquid hourly space velocity of 4.8 ml·(g cat)− 1·h− 1 over Ni/bentonite-20, providing 95.7% conversion of nitrobenzene and 98.8% selectivity of aniline. Higher dispersion and smaller crystallite size of metallic Ni are contributed to the batter catalytic performance. Ni/bentonite catalyst is a kind of promising catalyst in nitrobenzene hydrogenation process.Download full-size image

In-situ DRIFTS was used to study the deep oxidation of propane, a side reaction during propane oxidative dehydrogenation to propene. Strong adsorption of propene was supposed to be the main reason for the deep oxidation. It was found that gaseous oxygen in the feed and the reaction temperature had great influence on the reaction. To obtain a relative high selectivity to propene, the reaction temperature should be maintained at 150∼250 °C with a proper content of gaseous oxygen in the feed for a certain catalyst and some modifiers which could weaken the adsorption of propene on the catalyst surface would be favorable.

Combination of partial oxidation of methane (POM) with carbon dioxide reforming of methane (CRM) has been studied over Ru-based catalysts at 550 °C. POM, CRM and combined reaction were performed over 8wt%Ru/γ-Al2O3 and the results show that both POM and CRM contribute to the combined reaction, between which POM plays a more important role. Moreover, the addition of Ce to Ru-based catalyst results in an improvement in the activity and CO selectivity under the adopted reaction conditions. The Ce-doped catalyst was characterized by N2 adsorption-desorption, SEM, XRD, TPR, XPS and in situ DRIFTS. The mechanism has been studied by in situ DRIFTS together with the temperature distribution of catalyst bed. The mechanism of the combined reaction is more complicated and it is the combination of POM and CRM mechanisms in nature. The present paper provides a new catalytic system to activate CH4 and CO2 at a rather low temperature.

Microcapsules of salicylic acid (SA) with chitosan were prepared by spray drying method. Various analytical methods were used to characterize the nature of microcapsules. Fourier-transform infrared spectroscopy (FTIR) confirmed the presence of intermolecular interactions between chitosan and SA. Particle size analysis showed that the average size of microcapsules ranged from 2 to 20 μm. Scanning electron microscopy (SEM) studies indicated that the microspheres were spherical and had a relatively smooth surface. Microbiological assay of antibacterial activity for SA and its microcapsules was measured using different bacterial strains. It was found that the antibacterial activity of SA was improved after the formation of microcapsules. The in vitro release profile showed that the microcapsules could control SA release from 1 h to 4 h. Kinetic studies revealed that the release pattern follows Korsmeyer–Peppas mechanism. Enhanced antibacterial activity of the SA microcapsules was attributed to the synergistic effects of intermolecular hydrogen-bonding interactions N–H⋯O and O–H⋯OC between SA and chitosan. It was also confirmed by quantum chemical calculation.The enhanced release is attributed to the synergistic effects of intermolecular hydrogen-bond interactions CO⋯H–O and N⋯H–O between SA and chitosan.Download full-size image

Highly efficient solvent-free coupling reaction of carbon dioxide (CO2) and epichlorohydrin catalyzed by meso-tetraphenyl porphyrin magnesium (MgTPP) in the presence of triethylamine as co-catalysts is reported. As a chlorophyll-like catalyst, MgTPP showed excellent activity for the coupling reaction of CO2 and epichlorohydrin to chloropropene carbonate, in which the turnover number could reach up to 9200. Moreover, different factors including the amount of catalyst, reaction temperature, pressure and time were systematically investigated and the optimal reaction conditions were obtained (epichlorohydrin 50 mmol, MgTPP 5.0×10−3 mmol, triethylamine 6.25(10−3 mmol, 140 °C, 1.5 MPa, 8 h). A plausible two-pathway mechanism for the coupling reaction of CO2 and epichlorohydrin is proposed to propound the catalysis of MgTPP.

A facile and efficient procedure has been developed systematically for the oxidative cleavage of cinnamaldehyde to benzaldehyde by sodium hypochlorite with water as the only solvent in the presence of β-cyclodextrin (abbreviated as β-CD). Different factors influencing cinnamaldehyde oxidation e.g. reaction temperature, the amount of catalyst and oxidant, have been investigated. The yield of benzaldehyde reaches 76% under the optimum conditions (333 K, 4 h, molar ratio of cinnamaldehyde to β-CD is 1:1). Furthermore, a feasible reaction mechanism including the formation of benzaldehyde and the two main byproducts (phenylacetaldehyde and epoxide of cinnamaldehyde) has been proposed.

•Monolith-like Pt/AAO catalyst is applied to trace toluene combustion reaction.•Hot water treatment draws a significant effect on the performance of Pt/AAO catalyst.•Pt/HWT18 gives a comparable activity to Pt/γ-Al2O3 particle catalyst.Featuring an assembly of identical pores, through-pore anodic alumina (AAO) makes an ideal monolith-like catalyst support for volatile organic compound (VOC) combustion. This work employs the oxidation of toluene as a model reaction to investigate the applicability of AAO supported Pt catalysts in VOC catalytic combustion. In order to modify the microstructure of AAO, some AAO samples were exposed to hot water treatment (HWT) firstly. Results show that the optimum HWT time is 18 h. Pt/HWT18 gives a toluene conversion of 95% at 200 °C, which is comparable to the initial activity of commercial γ-Al2O3 particle supported Pt catalyst. Considering its confinement effect for the supported metal and its monolith-like compact unit, AAO support offers potential applications in VOC catalytic combustion.Download full-size image

Insoluble β-cyclodextrin polymers were prepared from β-cyclodextrin (β-CD) using epichlorohydrin (EPI) as crosslinking agent under basic conditions. The polymers were characterized by Fourier Transform Infrared (FTIR), Thermogravimetry (TG), X-ray diffraction (XRD) and TG-FTIR. The results demonstrated that the polymerization between EPI and β-CD indeed occurred, and a number of CD rings were interconnected to form a three-dimensional network. Moreover, different factors influencing the polymerization, e.g. molar ratio of EPI to β-CD, the concentration of NaOH and reaction temperature, have been investigated. The polymer prepared under the optimal conditions (the molar ratio EPI: β-CD of 44, the NaOH concentration 50% in mass, and the temperature at 65 °C) showed excellent thermal stability and insolubility in organic solvents or strong acid/base. In addition, the β-cyclodextrin polymers also presented high catalytic activity for aqueous oxidation of benzyl alcohol with hypochlorite as oxidant.

The cocatalytic effect of cobalt acetate on the manganese porphyrin-catalyzed oxidation of cyclohexene by molecular oxygen was investigated. The conversion of cyclohexene and the selectivity toward epoxide were significantly improved, whereas the formation of 2-cyclohexen-ol was restricted in the presence of the cocatalyst. A cocatalytic mechanism involving cobalt oxide ([Co–O2]+) as the active species for enhancing cyclohexene activity and selectivity toward epoxide was proposed.Highly efficient co-catalytic effect of cobalt acetate on the manganese porphyrin catalyzed cyclohexene aerobic oxidation has been achieved.Download full-size imageHighlights► Cocatalytic effect of Co(OAc)2 on MnTPPCl-catalyzed oxidation was observed. ► Conversion rising from 28% to 72% with Co(OAc)2 as cocatalyst was achieved. ► The valence of cobalt ion was kept unchanged during the reaction process.

•La and Ce made a great contribution in decreasing Cu outer-shell electron density.•La and Ce improved the reduction ability of Cu–Fe catalyst.•La-, Ce-modified Cu–Fe catalysts compared to Zr-modified Cu–Fe catalyst.•La-, Ce-modified Cu–Fe exhibit excellent stabilities in hydrogenation CO2 to DME.Cu–Fe–La/HZSM-5 and Cu–Fe–Ce/HZSM-5 bifunctional catalysts were prepared and applied for the direct synthesis of dimethyl ether (DME) from CO2 and H2. The catalysts were characterized by X-ray diffraction (XRD), N2 adsorption–desorption, H2-temperature programmed reduction (H2-TPR), and X-ray photoelectron spectroscopy (XPS). The results showed that La and Ce significantly decreased the outer-shell electron density of Cu and improved the reduction ability of the Cu–Fe catalyst in comparison to the Cu–Fe–Zr catalyst, which may increase the selectivity for DME. The Cu–Fe–Ce catalyst had a greater specific surface area than the Cu–Fe–La catalyst. This promoted CuO dispersion and decreased CuO crystallite size, which increased both the DME selectivity and the CO2 conversion. The catalysts were stable for 15 h.

•Pd/C with low loading efficiently catalyzes olefins epoxidation at ambient conditions.•Pd/C exhibits excellent stability and recyclability.•The epoxidation reaction on Pd/C is via radical intermediate.Epoxides are a kind of useful synthetic intermediates. This work reports that activated carbon-supported Pd nanoparticles (Pd/C) efficiently catalyzed cyclohexene epoxidation in the presence of molecular oxygen and isobutyraldehyde with 91.5% conversion, 95.6% selectivity to cyclohexene oxide, ~ 400 h− 1 activity and excellent stability for at least 5 catalytic runs. The epoxidation was examined on Pd catalysts supported on seven supports, and Pd/C exhibited superior catalytic performance possibly due to the inert support surface. The epoxidation reaction on Pd/C is via radical intermediate. Pd/C is also applicable to catalyze other olefins epoxidation.Download high-res image (102KB)Download full-size image

The cyclohexene epoxidation by molecular oxygen in the presence of tetraphenylporphyrin chloride of Mn, Fe, Co and Ru and isobutyraldehyde have been investigated. The results showed that high yield of epoxide was obtained by the liquid phase epoxidation of cyclohexene in the presence of isobutyraldehyde using Mn(TPP)Cl as catalyst. The reaction mechanism has been proposed, and the results indicated (according to the mechanism) that cyclohexene epoxide was mainly formed from the reaction of high-valent metal oxo intermediate with olefin directly, which was verified by in situ EPR and in situ UV–vis spectroscopy respectively. The factors influencing epoxide generation rate, e.g. the concentration of cyclohexene, manganese porphyrin catalyst and isobutyraldehyde, have been well investigated. The kinetics of cyclohexene aerobic epoxidation developed from the proposed mechanism was consistent with the experimental kinetics accurately.

Herein, we report a photoanode of g-C3N4/WO3 heterojunctions with exceptional ability and stability for photoelectrochemical (PEC) water splitting which achieved a high photocurrent density of 1.92 mA cm−2 at +1.23 V versus (vs.) RHE which is about 2 times higher than that of the pristine WO3 photoanode (0.71 mA cm−2).

Cost-effective catalysts for volatile organic compound (VOC) oxidation are critical to energy conversion and environmental protection. Herein, we developed new, low-cost and high-performance alkali-promoted 3D-NiCo2O4 nanosheet catalysts for HCHO oxidation at room temperature. Benefiting from the large surface area, high adsorption capacity and surface hydroxyls, the alkali-promoted 3D-NiCo2O4 nanosheet catalysts show substantially high catalytic activities for HCHO oxidation. The alkali-promoted 3D-NiCo2O4 nanosheets yield a remarkable HCHO conversion efficiency of 95.3% at room temperature, which is not achieved by any non-precious metal based catalysts at such low temperature. Additionally, the as-prepared alkali-promoted 3D-NiCo2O4 nanosheets retained excellent catalytic performance after 200 h, which can be applied to practical applications. This work provides a feasible approach to improve the efficiency of metal oxides for HCHO oxidation at low temperature.

Herein, we demonstrate a simple strategy to boost the photocatalytic performance of BiOI by introducing oxygen defects into the BiOI. The oxygen-deficient BiOI exhibits superior photocatalytic performance for the degradation of formaldehyde gas. The enhancement of photocatalytic activity is due to the enhanced separation and migration efficiency of photogenerated electrons and holes.

Hydrogen, a clean energy carrier with high energy capacity, is a very promising candidate as a primary energy source for the future. Photoelectrochemical (PEC) hydrogen production from renewable biomass derivatives and water is one of the most promising approaches to producing green chemical fuel. Compared to water splitting, hydrogen production from renewable biomass derivatives and water through a PEC process is more efficient from the viewpoint of thermodynamics. Additionally, the carbon dioxide formed can be re-transformed into carbohydrates via photosynthesis in plants. In this review, we focus on the development of photoanodes and systems for PEC hydrogen production from water and renewable biomass derivatives, such as methanol, ethanol, glycerol and sugars. We also discuss the future challenges and opportunities for the design of the state-of-the-art photoanodes and PEC systems for hydrogen production from biomass derivatives and water.