As an emerging class of porous crystalline materials, covalent organic frameworks (COFs) are excellent candidates for various applications. In particular, they can serve as ideal platforms for capturing CO₂ to mitigate the dilemma caused by the greenhouse effect. Recent research achievements using COFs for CO₂ capture are highlighted. A background overview is provided, consisting of a brief statement on the current CO₂ issue, a summary of representative materials utilized for CO₂ capture, and an introduction to COFs. Research progresses on: i) experimental CO₂ capture using different COFs synthesized based on different covalent bond formations, and ii) computational simulation results of such porous materials on CO₂ capture are summarized. Based on these experimental and theoretical studies, careful analyses and discussions in terms of the COF stability, low- and high-pressure CO₂ uptake, CO₂ selectivity, breakthrough performance, and CO₂ capture conditions are provided. Finally, a perspective and conclusion section of COFs for CO₂ capture is presented. Recent advancements in the field are highlighted and the strategies and principals involved are discussed.

Nanotechnology-based diagnostics and therapeutics usually suffer from long-term retention of nanosized devices in the major organs, which may cause unwanted side effects. Herein, we describe the development of ultra-small silica-polymer hybrid dots (Sdots) through the self-assembly between a polyethylene oxide-poly(propylene oxide)-polyethylene oxide (PEO-PPO-PEO) triblock copolymer and a silica precursor. Sdots feature a silica particle size of 4.2 nm and a hydrated size of 14 nm. The larger hydrated size is related to their polyethylene glycol (PEG) surface ligands, which evolve from the PEO blocks in the copolymer. The densely packed PEG corona can effectively shield the hybrid from reticuloendothelial uptake, which gives rise to rapid and thorough hepatobiliary clearance. In vivo experiments demonstrated that, upon intravenous injection, almost complete clearance of Sdots from mouse bodies could be realized through hepatobiliary excretion within only 5 days. Compared to renal clearable nanoparticles with short blood-circulation times, the proposed Sdots have a prolonged blood-circulation half-life of 19 h, so that the Sdots could effectively accumulate at a subcutaneous transplanted tumor through enhanced penetration and retention. As the PPO core of the Sdots can be utilized to accommodate hydrophobic guest molecules, such as anticancer drugs, these Sdots can prospectively serve as fast-clearable drug carriers for targeted cancer treatment.

Rapid developments in materials science and biological mechanisms have greatly boosted the research discoveries of new drug delivery systems. In the past few decades, hundreds of nanoparticle-based drug carriers have been reported almost on a daily basis, in which new materials, structures, and mechanisms are proposed and evaluated. Standing out among the drug carriers, the hybrid nanoparticle systems offer a great opportunity for the optimization and improvement of conventional chemotherapy. By combining several features of functional components, these hybrid nanoparticles have shown excellent promises of improved biosafety, biocompatibility, multifunctionality, biodegradability, and so forth. In this Personal Account, we highlight the recent research advances of some representative hybrid nanoparticles as drug delivery systems and discuss their design strategies and responsive mechanisms for controlled drug delivery.

Although near-infrared (NIR) light-absorbing organic dyes have recently been proposed for photothermal ablation of tumors, their clinical applications have often been hampered by problems such as low water solubility and minimal tissue absorption. Rapid development of nanotechnology provides various novel nanostructures to address these issues. In this work, doxorubicin (DOX)-loaded stealth liposomes are engineered through the incorporation of an NIR-absorptive heptamethine indocyanine dye IR825 into the thermoresponsive liposomes for photothermal/chemo combined cancer therapy. It is demonstrated that the lipid nanostructure can enhance the bioavailability of water-insoluble IR825 for efficient photothermal treatment, while delivering the anticancer drug doxorubicin to achieve simultaneous anticancer medication. The combined treatment of photothermal ablation and chemotherapy synergistically improves the overall cancer cell killing efficiency, which can be of future clinical interest.

Intracellular, reduction-responsive, amphiphilic, copolymer micelles with cancer cell specificity were developed. The copolymer was prepared with controlled molecular weight and functionalities using a double-headed initiator consisting of a disulfide linkage and folic acid targeting unit. The polymer could self-assemble into spherical micelles, which were stable under physiological conditions. Anticancer drug doxorubicin (DOX) was encapsulated into the micelles during the micellization and then released rapidly into the environment under the stimulus of intracellular reducing agent glutathione. Flow cytometry and confocal laser scanning microscopy observations further indicated that DOX was successfully released from the internalized micelles into the cytoplasm, inducing apoptosis and cell death. The potential of the present copolymer micelles for application as anticancer drug carriers for targeted cancer therapy is promising.

An imine-based nitrogen-rich covalent-organic framework (COF) was successfully synthesized using two triangular building units under solvothermal reaction condition. The gas adsorption properties of the obtained microporous nitrogen-rich COF were investigated. The results indicated that the activated COF material presented good up take capabilities of CO₂ and CH₄ at 61.2 and 43.4 cm³·g⁻¹ at 1 atm and 273 K, respectively, showing its application potential in selective gas capture and separation.

In this work, we developed a strategy to fabricate self-assembled aggregates encapsulating graphene from direct exfoliation of graphite. Naphthalene-anhydride-appended glutamic acid (NG) and pyrene-appended glutamic acid (PG) were utilized to exfoliate graphite to generate few-layer graphene in basic aqueous media. Acidification-triggered self-assembly of PG could encapsulate graphene sheets to give graphene@microsheet hybrids. Melamine (Mm) was introduced to induce the morphological transformation of PG from microsheets to twisted fibers with columnar packing. In the presence of graphene, this transformation allowed the fabrication of twisted-fiber-encapsulated graphene (graphene@twist fiber). Tricomponent hybrids were also built up via in situ preparation of gold nanoparticles (AuNPs) on the negatively charged surface of few-layer graphene during the self-assembly process. This study presents an approach to construct directly exfoliated graphene-based hybrids through self-assembly.

Glutamate receptor antagonists have been known to play a crucial role in the treatment of many neuronal diseases. Recently, these antagonists have also shown therapeutic effects in the treatment of cancer. In this study, an ionotropic glutamate (iGlu) receptor antagonist, 4-hydroxyphenylacetyl spermine (L1), was used concurrently with a common anticancer drug, doxorubicin (Dox), for simultaneous cancer therapy. Mesoporous silica nanoparticles (MSNPs) were employed as the delivery vehicle for both L1 and Dox by conjugating the iGlu receptor antagonist on the surface and encapsulating Dox within the mesopores. Dox was then trapped within the mesopores by functionalizing a redox-cleavable capping group on the MSNP surface, and it could be released upon exposure to the reductive glutathione. In vitro studies on B16F10 and NIH3T3 cell lines revealed that the iGlu receptor antagonist L1 exhibited therapeutic as well as targeting effects. In addition, the simultaneous use of therapeutic L1 and Dox proved to be synergistic in the treatment of cancer. The present work demonstrated the feasibility of employing a delivery system to deliver both neuroprotective drug and anticancer drug for efficient anticancer treatment.

Biomedical applications of nontoxic amorphous calcium carbonate (ACC) nanoparticles have mainly been restricted because of their aqueous instability. To improve their stability in physiological environments while retaining their pH-responsiveness, a novel nanoreactor of ACC–doxorubicin (DOX)@silica was developed for drug delivery for use in cancer therapy. As a result of its rationally engineered structure, this nanoreactor maintains a low drug leakage in physiological and lysosomal/endosomal environments, and responds specifically to pH 6.5 to release the drug. This unique ACC–DOX@silica nanoreactor releases DOX precisely in the weakly acidic microenvironment of cancer cells and results in efficient cell death, thus showing its great potential as a desirable chemotherapeutic nanosystem for cancer therapy.

A series of semiconducting polymer dots (Pdots) composed of phosphorescent Ir(III) complexes and polyfluorene units in the main polymer chains are designed, synthesized, and applied in ratiometric oxygen sensing and photodynamic cancer therapy. The ultrasmall Pdots with particle size less than 10 nm are fabricated in aqueous solution on account of amphiphilic nature of the polymers. The Pdots possess fine photostability, biocompatibility, and efficient energy transfer from the polymer main chain to the Ir(III) complex. By utilizing the excited-state energy transfer from phosphorescent Pdots to the ground state molecular oxygen, these Pdots are applied in the optical sensing of oxygen with ratiometric and naked-eye detection as well as high sensitivity in aqueous solution. The Pdots also show low cytotoxicity and can pass across the cell membrane to enter into the cytoplasm. The singlet oxygen photo-generated from the Pdots under irradiation at 488 nm can effectively induce the apoptosis and death of tumor cells for photodynamic cancer therapy in vitro.

Engineering multifunctional nanocarriers for targeted drug delivery shows promising potentials to revolutionize the cancer chemotherapy. Simple methods to optimize physicochemical characteristics and surface composition of the drug nanocarriers need to be developed in order to tackle major challenges for smooth translation of suitable nanocarriers to clinical applications. Here, rational development and utilization of multifunctional mesoporous silica nanoparticles (MSNPs) for targeting MDA-MB-231 xenograft model breast cancer in vivo are reported. Uniform and redispersible poly(ethylene glycol)-incorporated MSNPs with three different sizes (48, 72, 100 nm) are synthesized. They are then functionalized with amino-β-cyclodextrin bridged by cleavable disulfide bonds, where amino-β-cyclodextrin blocks drugs inside the mesopores. The incorporation of active folate targeting ligand onto 48 nm of multifunctional MSNPs (PEG-MSNPs48-CD-PEG-FA) leads to improved and selective uptake of the nanoparticles into tumor. Targeted drug delivery capability of PEG-MSNPs48-CD-PEG-FA is demonstrated by significant inhibition of the tumor growth in mice treated with doxorubicin-loaded nanoparticles, where doxorubicin is released triggered by intracellular acidic pH and glutathione. Doxorubicin-loaded PEG-MSNPs48-CD-PEG-FA exhibits better in vivo therapeutic efficacy as compared with free doxorubicin and non-targeted nanoparticles. Current study presents successful utilization of multifunctional MSNP-based drug nanocarriers for targeted cancer therapy in vivo.

Mn₃O₄ nanomaterials with different morphologies (sphere, nanowire, and octahedron) embedded into functionalized nanoporous polymers were developed by a facile one-pot solvothermal technique at different temperatures. These Mn₃O₄-based hybrid materials could behave as heterogeneous nanocatalysts to perform sp³ CH bond oxidation of aromatic hydrocarbons and alcohols with molecular oxygen as an economic oxidant. Catalytic activity could be effectively tuned by changing the morphology of incorporated Mn₃O₄ in nanoporous polymer. These Mn₃O₄-based hybrid materials exhibited remarkable catalytic performance for sp³ CH bond oxidation as compared with bare Mn₃O₄ nanoparticles. Mn₃O₄ with octahedral morphology in nanoporous polymer exhibited the highest catalytic activity on account of its more exposed crystallographic planes and edges. These Mn₃O₄-based nanocatalysts could be recycled and reused for consecutive catalytic cycles without a significant loss of catalytic activity.

A novel strategy for the synthesis of microporous crystalline titanosilicate catalyst (TS-1) was developed based on the combination of liquid-phase and solid-phase transformation mechanisms. The core concept of this strategy was to crystallize the mixed precursors composed of both liquid-phase and solid-phase precursors. The anionic polyelectrolyte poly(acrylic acid) was used as a unique gelating agent to prepare the solid/liquid mixture, which can partly convert the liquid-phase precursor to the solid-phase precursor. Active framework Ti was formed by in situ conversion of the Ti species from the solid-phase precursor during the crystallization stage, as well as by the transfer of Ti species from the liquid-phase precursor to the solid crystal after the crystallization. In this way, the content of active Ti in TS-1 was significantly increased. The obtained product displayed high activity for the oxidation reaction of n-hexane and 1-hexene.

Mesoporous silica nanoparticles (MSNPs) have been widely used as drug carriers for stimuli-responsive drug delivery. Herein, a catalysis screening technique was adopted for analyzing the effects of chain length, terminal group, and density of disulfide-appended functional ligands on the surface of MSNPs on drug-loading capacity and glutathione-triggered drug-release kinetics. The ligand with an intermediate length (5 carbon atoms) and a bulky terminal group (cyclohexyl) that complexes with theβ-cyclodextrin ring showed the highest drug loading capacity as well as good release kinetics. In addition, decreasing the surface coverage of the functional ligands led to an enhancement in drug release. In vitro drug-delivery experiments on a melanoma cell line (B16-F10) by using the functionalized MSNPs further supported the conclusion. The results obtained may serve as a general guide for developing more effective MSNP systems for drug delivery.

This study provides a successful preparation of biocompatible hybrid materials (1-GO and 2-GO) by the integration of graphene oxide (GO) with water-soluble pillararenes (bolaamphiphile 1 and tadpolelike amphiphile 2) for dual-mode Raman and fluorescence bioimaging in vitro. The investigations show that pillararenes 1 and 2 were loaded onto the surface of GO through strong hydrogen-bonding interactions. Aqueous suspensions of 1-GO and 2-GO are stable and can be kept for a long time. After confirming their good biocompatibility by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, the 1-GO and 2-GO hybrids were endocytosed by HeLa cells for in vitro Raman imaging. It was found that 1-GO presents better Raman imaging than 2-GO. When a fluorescent guest molecule, bipyridinium derivative 3, was added into the suspensions of the hybrids, the suspensions of 1-GO and 2-GO were as stable as the original. The suspensions of the inclusion complexes (1-GO⋅3 and 2-GO⋅3) formed from 1-GO and 2-GO with 3 can also be endocytosed by HeLa cells to enable in vitro fluorescence imaging to be performed. It was found that 1-GO⋅3 performs better than 2-GO⋅3. The current research has determined the capacities of pillararene-modified GO for combined bioimaging, which paves the way for using these biocompatible materials towards dual-mode diagnostics.

Developing gold nanoparticles (AuNPs) with well-designed functionality is highly desirable for boosting the performance and versatility of inorganic–organic hybrid materials. In an attempt to achieve ion recognition with specific signal expressions, we present here 4-piperazinyl-1,8-naphthalimide-functionalized AuNPs for the realization of quantitative recognition of Fe^III ions with dual (colorimetric and fluorescent) output. The research takes advantage of 1) quantity-controlled chelation-mode transformation of the piperazinyl moiety on the AuNPs towards Fe^III, thereby resulting in an aggregation–dispersion conversion of the AuNPs in solution, and 2) photoinduced electron transfer of a naphthaimide fluorophore on the AuNPs, thus leading to reversible absorption and emission changes. The functional AuNPs are also responsive to pH variations. This strategy for realizing the aggregation–dispersion conversion of AuNPs with returnable signal output might exhibit application potential for advanced nanoscale chemosensors.

A hollow mesoporous silica nanoparticle (HMSNP) based drug/siRNA co-delivery system was designed and fabricated, aiming at overcoming multidrug resistance (MDR) in cancer cells for targeted cancer therapy. The as-prepared HMSNPs have perpendicular nanochannels connecting to the internal hollow cores, thereby facilitating drug loading and release. The extra volume of the hollow core enhances the drug loading capacity by two folds as compared with conventional mesoporous silica nanoparticles (MSNPs). Folic acid conjugated polyethyleneimine (PEI-FA) was coated on the HMSNP surfaces under neutral conditions through electrostatic interactions between the partially charged amino groups of PEI-FA and the phosphate groups on the HMSNP surfaces, blocking the mesopores and preventing the loaded drugs from leakage. Folic acid acts as the targeting ligand that enables the co-delivery system to selectively bind with and enter into the target cancer cells. PEI-FA-coated HMSNPs show enhanced siRNA binding capability on account of electrostatic interactions between the amino groups of PEI-FA and siRNA, as compared with that of MSNPs. The electrostatic interactions provide the feasibility of pH-controlled release. In vitro pH-responsive drug/siRNA co-delivery experiments were conducted on HeLa cell lines with high folic acid receptor expression and MCF-7 cell lines with low folic acid receptor expression for comparison, showing effective target delivery to the HeLa cells through folic acid receptor meditated cellular endocytosis. The pH-responsive intracellular drug/siRNA release greatly minimizes the prerelease and possible side effects of the delivery system. By simultaneously delivering both doxorubicin (Dox) and siRNA against the Bcl-2 protein into the HeLa cells, the expression of the anti-apoptotic protein Bcl-2 was successfully suppressed, leading to an enhanced therapeutic efficacy. Thus, the present multifunctional nanoparticles show promising potentials for controlled and targeted drug and gene co-delivery in cancer treatment.

In this review, we highlight recent advancements on pillararene-based assemblies. The driving forces for the formation of the pillararene-based assemblies are discussed first. The host–guest interactions are deemed as not only general strategy for constructing assemblies but also essential components for preventing the assemblies from the dissociation. Solvent effect is also important in the assembling process, since it could influence the host–guest interactions and provide solvophobic effect on pillararenes for the assembly. Then, several pillararene-based assembly architectures are introduced, including pillararene-based interlocked structures, such as (poly)pseudorotaxanes, (poly)rotaxanes, and daisy chains, classified by their topological structures and synthetic strategy. The morphologies of the supramolecular assemblies are divided into several types, for example, nanospheres, nanotubes and supramolecular polymers. Furthermore, the functions and potential applications are summarized accompanied with related assembly structures. The review not only provides fundamental findings, but also foresights future research directions in the research area of pillararene-based assemblies.

The construction of physical or chemical adsorbents for CO₂ capture and sequestration (CCS) is a vital technology in the interim period on the way towards a sustainable low-carbon future. The search for efficient materials to satisfy the increasing demand for CCS has become extremely important. Porous materials, including porous silica, porous carbons, and newly developed metal–organic frameworks and porous organic polymers, possessing regular and well-defined porous geometry and having a high surface area and pore volume, have been widely studied for separations on laboratory scale. On account of the dipole–quadrupole interactions between the polarizable CO₂ molecule and the accessible nitrogen site, the investigations have indicated that the incorporation of accessible nitrogen-donor groups into the pore walls of porous materials can improve the affinity to CO₂ and increase the CO₂ uptake capacity and selectivity. The CO₂-adsorption process based on solid nitrogen-rich porous adsorbents does generally not require heating of a large amount of water (60–70 wt %) for regeneration, while such a heating approach cannot be avoided in the regeneration of amine-based solution absorption processes. Thus, nitrogen-rich porous adsorbents show good regeneration properties without sacrificing high separation efficiency. As such, nitrogen-rich porous materials as highly promising CO₂ adsorbents have been broadly fabricated and intensively investigated. This Focus Review highlights recent significant advances in nitrogen-rich porous materials for CCS.

Multifunctional mesoporous silica nanoparticles are developed in order to deliver anticancer drugs to specific cancer cells in a targeted and controlled manner. The nanoparticle surface is functionalized with amino-β-cyclodextrin rings bridged by cleavable disulfide bonds, blocking drugs inside the mesopores of the nanoparticles. Poly(ethylene glycol) polymers, functionalized with an adamantane unit at one end and a folate unit at the other end, are immobilized onto the nanoparticle surface through strong β-cyclodextrin/adamantane complexation. The non-cytotoxic nanoparticles containing the folate targeting units are efficiently trapped by folate-receptor-rich HeLa cancer cells through receptormmediated endocytosis, while folate-receptor-poor human embryonic kidney 293 normal cells show much lower endocytosis towards nanoparticles under the same conditions. The nanoparticles endocytosed by the cancer cells can release loaded doxorubicin into the cells triggered by acidic endosomal pH. After the nanoparticles escape from the endosome and enter into the cytoplasm of cancer cells, the high concentration of glutathione in the cytoplasm can lead to the removal of the β-cyclodextrin capping rings by cleaving the pre-installed disulfide bonds, further promoting the release of doxorubicin from the drug carriers. The high drug-delivery efficacy of the multifunctional nanoparticles is attributed to the co-operative effects of folate-mediated targeting and stimuli-triggered drug release. The present delivery system capable of delivering drugs in a targeted and controlled manner provides a novel platform for the next generation of therapeutics.

A mesoporous silica nanoparticle (MSNP) based co-delivery system is developed in order to deliver simultaneously drug and single strand DNA (ssDNA) in a controlled manner. Negatively charged ssDNA as a model gene is immobilized onto the surface of positively charged ammonium-functionalized MSNPs through electrostatic interaction, effectively blocking the loaded drugs within the mesopores of MSNPs. When the pre-installed disulfide bond on the ammonium unit is broken by the addition of the reducing agent such as dithiothreitol or glutathione, the ssDNA network on the surface is freed, leading to the release of the loaded drug molecules from the mesopores. The cell investigations indicate that the functional nanoparticles have a very low cytotoxicity under the concentrations measured. The doxorubicin-loaded and ssDNA-coated nanoparticles show an enhanced cellular internalization, leading to a successful drug/ssDNA co-delivery in vitro for significant apoptosis of Hela cancer cells as compared with that of free doxorubicin. The obtained experimental results indicate promising applications of the functional nanoparticles in cancer treatment.