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Cu+-containing materials have shown various application prospects especially in adsorption and catalysis, because they are versatile, non-toxic and low cost. To date, developing a mild and controllable approach for the fabrication of Cu+ sites has remained a pronounced challenge. Herein, we report a series connection double-solvent strategy (SCDS) for fabricating Cu+ sites within MIL-101(Cr), a typical metal–organic framework. By employing the SCDS in which vitamin C is chosen as the environmentally benign reducing agent, Cu2+ was incorporated in the pores and then transformed to Cu+ in the confined spaces. Compared to the conventional high-temperature autoreduction method conducted under harsh environment (700 °C for 12 h) with a low Cu+ yield (less than 50%), SCDS can selectively reduce Cu2+ to Cu+ at room temperature without generating any Cu0. The resulting Cu+ modified MIL-101(Cr) exhibits good desulfurization performance in view of both uptake and recyclability.

Ordered porous solid strong bases (OPSSBs) have attracted great research interest due to the excellent performance as heterogeneous catalysts in various reactions. The main obstacle for fabricating OPSSBs is the requirement of high temperature to produce strong basicity on ordered porous materials. For example, the temperatures of 600–650 °C are required for the decomposition of base precursor NaNO3 to basic sites on mesoporous silica SBA-15 and zeolite Y. Such high decomposition temperatures are energy-intensive and harmful to the structure of supports. Herein, we report the fabrication of OPSSBs by utilizing the redox interaction between base precursor and low-valence metal centers (e.g., Cr3+) in metal-organic frameworks (MOFs). The base precursor NaNO3 on MIL-101(Cr) can be converted to basic sites entirely at 300 °C, which is quite lower than those of the conventional thermal conversion on SBA-15 and zeolite Y (600–650 °C). The exploration on decomposition mechanism reveals that the valence change of Cr3+ to Cr6+ takes place during the conversion of NaNO3 to basic sites. In this way, MOFs-derived base catalysts have been synthesized successfully by the host–guest redox strategy and exhibit high catalytic activity in typical base-catalyzed reactions.

Porous liquid is a unique liquid medium that combines permanent porosity of porous solid with the fluidity of liquid, and this special characteristic makes it potential in various applications. Here we report the first photoresponsive porous ionic liquid (PPIL) by solubilizing photoresponsive metal-organic polyhedron (PMOP, constructed from dicopper and azobenzene-containing carboxylate) in polyethylene-glycol-functionalized bulky ionic liquid (IL). Owing to favorable ion interactions, bulky IL molecules encircle outside PMOP cages, and the inter cavities are maintained. The azobenzene moieties can be isomerized freely in the obtained PPILs to expose and shelter active sites upon visible and UV light irradiations. Hence, the adsorption capacity of PPILs is controllable by light irradiation, and the change in CO2 uptake is up to 30% which is different from neat IL with negligible change. This study might inspire the development of new adsorption process regulated by light instead of conventional pressure and temperature swing adsorption technologies.

Solid superbases can catalyze diverse reactions under mild conditions, while they suffer from aggregation of basic sites and poor stability during recycling. Here we report a new generation of solid superbases derived from K single atoms (SAs) prepared by a tandem redox strategy. The initial redox reaction takes place between base precursor KNO

Solid strong bases can catalyze a variety of organic reactions under mild conditions. Their preparation consists of loading base precursors (e.g. KNO3) on porous supports followed by activating to convert base precursors to basic sites (e.g. K2O). However, high temperatures are usually required for activation, which consumes lots of energy and damages the structure of supports. Moreover, filtration or centrifugation is mainly adopted for the recovery of solid base catalysts, which is tedious and limits their applications to some extent. In this paper, we constructed multifunctional core–shell structured Fe3O4@C microspheres as the supports owing to the reducibility of carbon shell and the magnetism of Fe3O4 core, thus creating magnetically responsive solid strong bases under mild conditions. Strong basic sites can be formed at a low temperature of 400 °C due to the redox reaction between the carbon shell and the base precursor, yielding the solid base K-400@Fe3O4@C. Such a temperature is obviously lower than the temperature for the decomposition of KNO3 on the frequently used supports SiO2 (750 °C) and Al2O3 (500−700 °C). The resultant solid base K-400@Fe3O4@C exhibits excellent catalytic activity in transesterification reaction, and the yield of target product dimethyl carbonate is higher than some benchmarks like MgO, CsX, and Na2O/Al2O3. In addition, thanks to the superparamagnetism, the solid base catalysts can be recovered within 10 s with the assistance of external magnetic fields.

Metal-organic frameworks (MOFs) have attracted increasing research enthusiasm owing to their tunable functionality, diverse structure characteristics, and large surface area. However, poor hydrothermal stability restricts the utilization of some MOFs in practical applications. Our work aims at improving the hydrothermal stability of a representative MOF, namely, HKUST-1, by incorporating a two-dimensional material Ti3C2Tx MXene for the first time. A new type of hybrid material is synthesized through the hybridization of HKUST-1 and Ti3C2Tx, and the obtained hybrids show improved hydrothermal stability as well as catalytic performance. The porosity of hybrids is enhanced when incorporating an appropriate amount of Ti3C2Tx, and the surface area can reach 1380 m2·g-1, while the pristine HKUST-1 is 1210 m2·g-1. After the hydrothermal treatment (hot water vapor, 70 °C), the structure of hybrid materials maintains well, while the framework of HKUST-1 is severely destroyed. When catalyzing the ring-opening reaction of styrene oxide, the conversion reaches 76.7% only for 20 min, which is much higher than that of pure HKUST-1 (23.1% for 20 min). More importantly, the catalytic activity could recover without loss even after six cycles. Our hybrid materials are promising in practical catalytic applications due to their excellent hydrothermal stability, catalytic activity, and reusability.

Reproducing the highly efficient catalytic cascade system to mimic life behaviors in vitro has been intensively investigated over the past few decades. However, except for biocatalysis with enzymes, most chemocatalytic cascades in essence combine several reactions that occur over mutually independent catalytic sites in a container. Herein, with a series of control experiments and stepwise theoretical derivation based on the calculations of density functional theory and a semi-empirical method, a generalized cascade catalysis is discovered for the chemocatalytic conversion of CO2 to higher alcohols over a porphyrinic zirconium metal–organic framework, PCN-224-Cu. Two types of catalytic sites in PCN-224-Cu, i.e., the Zr6 cluster and TCPP-Cu unit, act like organelles, which can complete a class of reactions instead of particular one. The Zr6 cluster is in charge of molecular dissociation, while the TCPP-Cu unit is responsible for molecular assembly. Therefore, semi-finished intermediates repeatedly transfer between the two types of catalytic sites until the ultimate formation of ethanol with high efficiency (ethanol yield, 4.53 mmol h−1 gcat.−1 at 403 K) and selectivity (∼100%).

Palladium (Pd)-containing catalysts have gained extensive attention because of their outstanding activity in various heterogeneous catalytic reactions. The activity of these catalysts highly correl...

With the carbonization at an elevated temperature, high aromaticity of a precursor for porous carbons was traditionally thought to be crucial for the resultant perfect textural properties and ideal application performances of the porous carbons. Thus, many efforts have been done to search or to artificially prepare the polymer precursors with higher aromaticity to generate more satisfying porous carbons. However, an antiempirical case was found in this study. The copolymerization between 1,3,5-tris(chloromethyl)-2,4,6-trimethylbenzene (TCM) and cyclohexane-1,4-diamine was successfully implemented to get a polymer code-named NUT-40, in which half of the ring structures are nonaromatic, while N-doped porous carbons (NDPCs) with better textural properties (e.g., SBET = 1363 m2 g−1 for NDPC-600) and competitive CO2 capture abilities (e.g., CO2 capacity = 4.3 mmol g−1 at 25 °C and 1 bar for NDPC-600) were generated from the NUT-40, compared with the NDPC counterparts derived from the NUT-4 in a previous study (e.g., SBET = 958 m2 g−1 and CO2 capacity = 3.8 mmol g−1 at 25 °C and 1 bar for NDPC-600), in which TCM and ursol were employed as the monomers instead, and thus the ring structures in the NUT-4 was fully aromatic. With first-principle and molecular dynamics simulations, it was demonstrated that the embryo pore structure in the NUT-40 molecule can be more easily maintained during the carbonization than that of the NUT-4, which finally improves the surface area and porosity of the NUT-40 generated NDPCs.

Hierarchically porous metal-organic frameworks (HP-MOFs) are promising in various applications. Most reported HP-MOFs are prepared based on the generation of mesopores in microporous frameworks, and the formed mesopores are connected by microporous channels, limiting the accessibility of mesopores for bulky molecules. A hierarchical structure is formed by constructing microporous MOFs in uninterrupted mesoporous tunnels. Using the confined space in as-prepared mesoporous silica, highly dispersed metal precursors for MOFs are coated on the internal surface of mesoporous tunnels. Ligand vapor-induced crystallization is employed to enable quantitative formation of MOFs in situ, in which sublimated ligands diffuse into mesoporous tunnels and react with metal precursors. The obtained hierarchically porous composites exhibit record-high adsorption capacity for the bulky molecule trypsin. The thermal and storage stability of trypsin is improved upon immobilization on the composites.

Porous materials like metal–organic frameworks are crucial matrixes to construct heterogeneous catalysts for energy conversion. To maximize the efficiency, it is desirable that the properties of po...

Reducing the nitrogen-containing compounds (NCCs) in fuel oils to ultralow level is essential for preventing the oil refining catalysts from being poisoned and for protecting the environment. Adsorptive denitrogenation is proved to be an effective mean to reduce the NCCs content. Herein, a series of N-doped porous carbons (NDPCs) in possession of proper pore structures, large surface area and moderate N species, which is verified through a series of characterization, are synthesized on the basis of the precursor copolymerized between 2,4,6-tris(chloromethyl)mesitylene and ethylenediamine. The NDPC-700 produced from the copolymer carbonization at 700 °C exhibits a record high adsorptive capacity of 7.35 mmol·g−1 for indole in the model oils, and the stable performance on the NCC adsorption is observed after 10 cycles of regeneration and reusage. The excellent adsorption capacity is attributed to the synergistic effect between porosities and N-containing sites. Moreover, the first-principle simulation proves that the N species, in particular the N-5 species, is helpful to the improvement of the adsorption capacity for indole.

Mesoporous solid strong bases are quite attractive due to their good catalytic performance for applications as environmentally friendly catalysts in various reactions. However, pretty harsh conditions are usually compulsory for the fabrication of strong basicity by using traditional thermal activation (e.g., 700 °C for the activation of base precursor KNO3 supported on mesoporous Al2O3). This is energy intensive and harmful to the mesoporous structure. In this study, we report a strategy of endowing supports with reducibility (ESWR) by doping low-valence Cr3+ into mesoporous Al2O3, so that the activation temperature for basicity generation is decreased significantly. Fascinatingly, KNO3 on mesoporous Al2O3 can be motivated to basic sites completely at the temperature of 400 °C via the ESWR strategy, which is much lower than the conventional thermal activation (700 °C). We have demonstrated that the redox reciprocity between KNO3 and Cr3+ is responsible for the low-temperature conversion, and Cr6+ is formed quantitatively as the oxidation product. The obtained solid bases possessing ordered mesostructure and strong basicity provide promising candidates for base-catalyzed synthesis of dimethyl carbonate via transesterification. The catalytic activity is obviously higher than a typical solid base like MgO as well as a series of reported basic catalysts containing alkali metal and alkaline-earth metal oxides.

Photoresponsive metal-organic polyhedra (PMOPs) have attracted expanding interests due to their modular nature with tunable functionality and variable responsive behaviors tailored conveniently by external-stimulus. However, their photoresponsive efficiency is often compromised after activation because of desorption-triggered aggregation into bulk PMOPs, which limits their utility in stimuli-responsive applications. Here, we report a case system that can overcome the aggregation problem and achieve maximized photoresponsive efficiency by polyhedral isolation in the nanoscaled spaces of mesoporous silica (MS). Through confinement, amount-controllable PMOPs are well dispersed in the nanoscaled spaces of MS, avoiding aggregation that commonly takes places in bulk PMOPs. Furthermore, reversible trans/ cis isomerization of photoresponsive groups can be realized freely during ultraviolet/visible light irradiation, maximizing control over photoresponsive guest adsorption behaviors. Remarkably, after trans/ cis isomerization, the confined PMOP-1 shows 48.2% of change in adsorption amount for propene with small molecular size and 43.9% for brilliant blue G (BBG) with large molecular size, which is significantly higher than that over bulk PMOP-1 with 11.2% for propene and 7.8% for BBG, respectively. Therefore, our work paves a way for the design and construction of multifunctional composite materials toward efficient stimuli-responsive needs.

Photoresponsive metal-organic frameworks (PMOFs) are of interest for tailorable CO2 adsorption. However, modulation of CO2 adsorption on PMOFs is based on steric hindrance or structural change owing to weak interactions between CO2 and active sites. It is challenging to fabricate PMOFs with strong but tailorable sites for CO2 adsorption. Now, the construction of PMOFs with target-specific (strong) active sites is achieved by introducing tetraethylenepentamine into azobenzene-functionalized MOFs for tailorable CO2 adsorption. Amines are specific active sites for CO2 , contributing to capture CO2 selectively. Cis/trans isomerization of azobenzene motifs trigged by UV/Vis light adjusts the electrostatic potential of amines significantly, leading to exposure/shelter of amines and modulation of CO2 adsorption on strong active sites. This system enables us to design adsorption processes for CO2 capture from mixtures, which is impossible to realize by traditional PMOFs.

Cobalt-based catalysts are highly promising for the oxygen evolution reaction (OER) in terms of both cost and performance. The dispersion state of Co3O4 impacts the catalyst performances directly, while development of an efficient method for Co3O4 dispersion remains a pronounced challenge. In this study, it is the first time that the confined space strategy (CSS) is employed to make highly dispersive Co3O4 on the mesoporous silica (MS) SBA-15. The precursor of Co3O4 is successfully introduced into the confined space inherent in as-prepared SBA-15 (between the silica walls and the template). The CSS facilitates the formation of Co3O4 with extremely high dispersion after the decomposition of Co precursor. Up to 4 mmol of Co3O4 can be dispersed in per gram of MS without any X-ray diffraction lines (the obtained sample is denoted as 4CoAS), while obvious diffraction lines are detected in the counterpart prepared from calcined SBA-15 (the sample is denoted as 4CoCS). Further calculation indicates that the size...

Transparent thermo-responsive poly(N-isopropylacrylamide)-l-poly(ethylene glycol)acrylamide (PNIPAM-l-PEG) conetwork hydrogels with rapid deswelling response are prepared by using multi-arm star poly(ethylene glycol)acrylamide (multi-arm star PEGAAm) molecules as cross-linkers. The introduction of multi-arm star PEGAAm cross-linkers can restrain the formation of dense skin layers on the surface of PNIPAM-l-PEG hydrogels, and act like water channels to facilitate the release of water from the hydrogels, resulting in rapid deswelling response. Meanwhile, the internal conetwork structures of the PNIPAM-l-PEG hydrogels are much more homogeneous due to the regular chemical structures of the multi-arm star PEGAAm cross-linkers. The cross-linkers can directly cross-link PNIPAM chains and serve as the backbones of the conetworks. This reduces the strong aggregation of hydrophobic PNIPAM chains against the formation of heterogeneous microstructures within the hydrogels during the deswelling process, leading to the maintenance of their transparency even at a temperature higher than their gel collapse temperature (GCT). The transparent PNIPAM-l-PEG hydrogels with rapid deswelling response show great potential for engineering advanced sensors and devices for optical applications.

The photo-induced polymerization to covalently link metal-organic polyhedra (MOPs) by flexible polymer chains is reported for the first time, which endows MOPs with enhanced processability, dispersity, and hydrostability. The resultant hybrid material exhibits 9 times higher capacity and much better reusability than bulk MOPs in the adsorption of methylene blue.

The catalytic active sites over the universal Cu-ZnO based catalysts for CO2 hydrogenation to methanol are still the subject of intense debate. Herein, unified first-principle calculations for the CO2 conversion processes over the controversial catalytic active sites, i.e., Cu crystal steps, Zn-doped Cu sites, Cu/ZnO interfaces, and the Cu and Zn closest packing crystal facets, are implemented, which is verified with the experimental facts based on support-free catalysts of porous hollow nanospheres that eliminate the interferences from the catalyst supports. We discover that the enhanced catalytic activity corresponds to the uplifted and spin-polarized density of states owing to the hybridization of Cu and Zn species, and prove that Cu/ZnO interfaces and Zn-doped Cu sites play significant roles among the catalytic active sites, and successively participate in the CO2 conversion, of which initial step should primarily be the hydrogen-free CO2 dissociation, differing from the preconceived viewpoint of hydrogen-assisted dissociation of CO2.

Metal–organic frameworks (MOFs) have drawn much attention for their highly promising applications, but the applications are often obstructed by the congenitally hydrothermal instability of the MOFs. Hybridizing the MOFs with other materials has been proved to be effective to solve the hydrothermal problems. Herein, a vapor-induced crystallization (VIC) method is employed for the first time to fabricate the hybrid MOFs based on the Cu-BTC and the natural clay attapulgite (NCA). Compared with the traditional solvothermal method for the hybridization, the VIC one has the obvious advantages of both reducing the solvent consumption and inducing the crystals self-repairing to generate perfect crystals of the hybrid MOFs. With an appropriate content of the NCA, the hybrid MOFs are proved to be highly stable even undergoing the hot water vapor (90 °C) for 12 h. The hybrid MOFs also exhibit the improved catalytic activity in catalyzing the styrene oxide ring-opening. The molar conversion of the styrene oxide over ...

The catalytic activity of supported noble metal nanoparticles (NPs) is strongly dependent on their size. However, it is still a pronounced challenge to develop a facile method to reduce the size of noble metal NPs. Here we report a facile but efficient strategy by utilizing confined spaces between templates and silica walls in as-prepared SBA-15 (AS) to regulate the size of a well-known noble metal, rhodium (Rh). Rh NPs formed in confined spaces possess obviously smaller size than their counterparts generated in traditional calcined SBA-15 (CS) without confined spaces. Our results also demonstrate that the obtained materials are highly active in CO oxidation. For a typical material 5.0RhAS containing 5.02 wt % of Rh, the complete conversion of CO is achieved at 70 °C, which is evidently lower than that of its analogue 5.0RhCS (102 °C).

Heterogeneous strong base catalysts possessing ordered nanoporous structure are highly expected due to their high activity and shape selectivity in diverse reactions. However, their fabrication remains a great challenge because quite high temperatures (600–700 °C) are compulsory for the generation of strong basicity on conventional ordered nanoporous materials (i.e., zeolites and mesoporous silicas). Here, we report for the first time direct fabrication of strong basic sites on metal–organic frameworks (MOFs) by using guest–host redox (GHR) interaction between base precursors and low-valence metal centers (e.g., Cr3+), which breaks the tradition of thermo-induced decomposition of base precursors. It is fascinating that base precursor KNO3 can be converted to strong basic species on MIL-53(Cr) at 300 °C, which is much lower than that on zeolite Y (700 °C) and mesoporous silica SBA-15 (600 °C). The resultant solid base exhibits strong basicity, ordered nanoporous structure, and high activity and shape selec...

With the growing demand for green chemistry, mesoporous solid strong bases have attracted increasing attention in view of their tremendous potential as eco-friendly catalysts in diverse reactions. In the present study, K-incorporated mesoporous carbon is successfully prepared through high-temperature chemical activation combined with the hard-templating method. The combined method is proved to be very effective at promoting the formation of stable K species that strongly interact with the carbon support. The obtained solid bases thus have both high activity and enhanced water-resistant stability, which is reflected in their catalysis of the transesterification of ethylene carbonate with methanol to dimethyl carbonate. A much higher turnover frequency (TOF) value (430.4 h−1) and better reusability are thus observed, compared with a series of typical and popular solid bases, such as MgO (TOF, 1.0 h−1) and CaO/SBA-15 (TOF, 6.4 h−1).

Great attention has been given to metal-organic frameworks (MOFs)-derived solid bases because of their attractive structure and catalytic performance in various organic reactions. The extraordinary skeleton structure of MOFs provides many possibilities for incorporation of diverse basic functionalities, which is unachievable for conventional solid bases. The past decade has witnessed remarkable advances in this vibrant research area; however, MOFs for heterogeneous basic catalysis have never been reviewed until now. Therefore, a review summarizing MOFs-derived base catalysts is highly expected. In this review, we present an overview of the recent progress in MOFs-derived solid bases covering preparation, characterization, and catalytic applications. In the preparation section, the solid bases are divided into two categories, namely, MOFs with intrinsic basicity and MOFs with modified basicity. The basicity can originate from either metal sites or organic ligands. Different approaches used for generation of basic sites are included, and each approach is described with representative examples. The fundamental principles for the design and fabrication of MOFs with basic functionalities are featured. In the characterization section, experimental techniques and theoretical calculations employed for characterization of basic MOFs are summarized. Some representive experimental techniques, such as temperature-programmed desorption of CO

The types and quantities of active sites play a critical role in catalysis. Herein, ZnO nanoparticles encapsulated into N-doped porous carbon has been rationally prepared by the pyrolysis of a metal-organic framework (MOF) followed by a moderate oxidation treatment. The resulting catalyst exhibits excellent activity, selectivity, and recyclability in the CO2 cycloaddtion reactions with epoxides owing to the synergy of multiple sites inherited from the MOF and generated by the oxidation process.

Au-containing catalysts are highly active in diverse reactions, and their activity strongly depends on the dispersion degree of Au. Here we report for the first time a solid-phase reduction strategy to promote Au dispersion in template-occluded SBA-15 (AS) by fully considering three crucial factors, namely (i) the interaction between Au and supports, (ii) the space where Au precursors locate during reduction, and (iii) the reduction method. First , both template and silica walls in AS offer interaction with Au species. Second , AS presents confined spaces between template and silica walls. Third , the reduction in solid phase avoids the competitive adsorption of solvent molecules. The results show Au-containing AS has a better dispersion of Au than its counterpart prepared from template-free SBA-15 (CS). Moreover, the obtained materials exhibit excellent catalytic activity in reduction reactions and that the organic template retained in mesopores promotes the reactions greatly.

A smart adsorbent RA@MS is fabricated by incorporating a di-block copolymer through the combination of the thermo-responsive block poly(N-isopropylacrylamide) (R) and the active block poly{N-[3-(dimethylamino) propyl]methacrylamide} (A, tertiary amines as basic sites) into mesoporous silica. The di-block copolymer RA preserves the thermo-responsive nature, which makes the active sites reversibly exposed/blocked in light of temperature variation. The obtained adsorbent possessing thermo-responsive properties can thus realize both selective adsorption and efficient regeneration for temperature-swing adsorption (TSA) of dyes.

Poor dispersity and low stability are two predominant shortcomings hindering the applications of metal–organic polyhedra (MOPs). The confinement of MOPs in nanoscale cavities of mesoporous matrices is efficient in overcoming both shortcomings, while the improvement of the current double-solvent method is highly expected. Here we develop a facile, controllable strategy to fabricate three MOPs (coordinated from dicopper and carboxylates) in confined cavities via in situ site-induced assembly (SIA), for the first time. The cavities of mesoporous matrix SBA-16 were pre-functionalized with amine sites, which induce in situ assembly of precursors that diffused into cavities. Hence, both the amount and location of MOPs in the mesoporous matrix can be easily controlled. Upon confinement, the dispersity, stability, and catalytic performance (on ring-opening reactions) of MOPs are greatly improved. Moreover, the enhancement of stability makes it possible to observe MOPs using high-resolution transmission electron microscopy (HRTEM) directly.

Catalysis benefits from biomimetic materials with sophisticated structures because a variety of functions can be integrated into one structure, satisfying the demands of a diverse range of applications. Magnetic catalysts have been widely used in various applications, but the magnetic components are most commonly used for recycling. In this study, we report the fabrication of magnetic nanocatalysts composed of a support of magnetic nanobars and Ag nanoparticles confined between two silica layers. Notably, the catalysts are constructed as nanoscale stirring bars that are able to generate disturbances at this scale. More importantly, the catalysts can be applied in both macro- and micro-systems, effectively addressing the conventional mixing method. The catalysts can then be conveniently separated from the system after use. The performances of magnetic nanoscale catalysts are well maintained through recycling.

Hierarchically porous metal-organic frameworks (HP-MOFs) have attracted great attention owing to their advantages over microporous MOFs in some applications. Despite many attempts, the development of a facile approach to generate HP-MOFs remains a challenge. Herein we develop a new strategy, namely the modulation of cation valence, to create hierarchical porosity in MOFs. Some of the CuII metal nodes in MOFs can be transformed into CuI via reducing vapor treatment (RVT), which partially changes the coordination mode and thus breaks coordination bonds, resulting in the formation of HP-MOF based on the original microporous MOF. Both the experimental results and the first-principles calculation show that it is easy to tailor the amount of CuI and subsequent hierarchical porosity by tuning the RVT duration. It is found that the resultant HP-MOFs perform much better in the capture of aromatic sulfides than the original microporous MOF.

Because of their abundant porosity, tunable surface properties, and high stability, N-doped porous carbons (NPCs) are highly promising for CO2 capture. Carbonization of N-containing polymers is frequently used for the preparation of NPCs, while such an approach is hindered by the high cost of some polymer precursors. In the present study, we report for the first time the fabrication of NPCs through the rational choice of the low-cost, N-rich polymer NUT-2 (NUT indicates Nanjing Tech University) as the precursor, which was obtained from polymerization of easily available monomers under mild conditions in the absence of any catalysts. Through carbonization at different temperatures (500–800 °C), NPCs with various porosity and nitrogen contents are obtained. The pore structure and CO2-philic (N-doped) sites are responsible for the adsorption performance, while the highest surface area does not lead to the highest CO2 adsorption capacity. For the sample carbonized at 600 °C (NPC-2-600), the adsorption capacit...

Metal-organic polyhedra (MOPs) have attracted great attention due to their intriguing structure. However, the applications of MOPs are severely hindered by two shortcomings, namely low dispersity and poor stability. Here we report the introduction of four MOPs (constructed from dicopper and carboxylates) to cavity-structured mesoporous silica SBA-16 via a double-solvent strategy to overcome both shortcomings simultaneously. By judicious design, the dimension of MOPs is just between the size of cavities and entrances of SBA-16, MOP molecules are thus confined in the cavities. This leads to the formation of isolated MOPs with unusual dispersion, making the active sites highly accessible. Hence, the adsorption capacity on carbon dioxide and propene as well as catalytic performance on ring opening are much superior to bulk MOPs. More importantly, the structure and catalytic activity of MOPs in confined cavities are well preserved after exposure to humid atmosphere, whereas those of bulk MOPs are degraded seriously.

Due to its low cost and easy availability, the natural clay, attapulgite (ATP), is a promising substitute of relatively expensive zeolites for adsorption and catalysis. However, the narrow porous network of ATP hinders its practical applications severely. In the present study, a tandem demetalization–desilication strategy was developed to enhance porosity of ATP by adding NH 4 F followed the HCl treatment, for the first time. The HCl treatment leaches out the cations (including Mg, Ca, Al, and Fe) in octahedral sheets and generates silicon products, which block the pores of ATP. The subsequent addition of NH 4 F leads to the formation of a buffer solution, which is efficient in the removal of silicon products. As a result, abundant secondary porosity is created, which induces an obvious increase of surface area from 128 to 232 m 2 g −1 and pore volume from 0.38 to 0.77 cm 3 g −1 . The preliminary applications of the obtained material in adsorption and catalysis were also tested. The material exhibits obviously better performance in the selective adsorption of CO 2 from CH 4 and N 2 than pristine ATP, and the adsorption amount of CO 2 increases sharply from 23.5 to 57.5 mg g −1 . In the Friedel–Crafts alkylation reaction of benzyl bromide with toluene, the obtained material can catalyze the conversion of 99.2% of benzyl bromide, which is 3.3 times as high as that catalyzed by pristine ATP. These properties make the obtained material highly promising in substituting zeolites for various applications.

A new generation of smart adsorbents was designed by grafting photo-responsive molecules onto the pore entrances of mesoporous silica. These molecules act as the gates of the mesopores, which are reversibly closed/opened upon light irradiation. Our smart adsorbents thus realize both selective adsorption and efficient desorption, which is highly expected for adsorption but impossible for traditional adsorbents with fixed pore entrances.

Functionalization of metal–organic frameworks (MOFs) with Cu(I) sites is extremely desirable for various applications including adsorption, catalysis, and sensing. The traditional method for the conversion of supported Cu(II) to Cu(I) is high-temperature autoreduction (HTA), which produces Cu(I) with an unsatisfactory yield (ca. 50%) but requires quite harsh conditions (e.g. 700 °C, 12 h) that are unsuitable for MOFs. Here we report the rational design of an efficient, controllable strategy for the conversion of supported Cu(II) to Cu(I) by using vapor-induced selective reduction (VISR), in which vapors of weak reducing agents (e.g. methanol) diffuse into the pores of MOFs and interact with Cu(II) precursors. This strategy allows the fabrication of Cu(I) sites with a 100% yield without the formation of Cu(0) at much lower temperatures (e.g. 200 °C, 6 h) and subsequently preserves the structure of MOFs well. Due to the abundant Cu(I) sites and high porosity of MOF supports, the obtained materials exhibit excellent performance in adsorptive desulfurization with regard to capacity, selectivity, and recyclability.

The dry reforming of CH4 (DRM) with CO2 has received much attention due to the utilization of two green-house gases for the production of syngas. Nickel-containing catalysts have been applied widely in DRM due to their considerable catalytic activity and relative affordable cost, and the activity of catalysts relies on the dispersion of Ni species. Here we developed a nanoconfinement strategy to facilitate the dispersion of NiO in nanoconfined spaces provided by as-made SBA-15 (AS) occluded with the template. The Ni precursor can be inserted into the nanoconfined spaces between silica walls and template in AS by grinding, and in subsequent calcination for NiO formation, aggregation that takes place in conventional calcined SBA-15 (CS) without template can be effectively avoided. Our results show that a high amount of NiO (4 mmol/g, 23 wt%) can be well dispersed in the material from AS (denoted as NiAS), while serious aggregation occurs for the material from CS with the same NiO loading (denoted as NiCS). We also demonstrate that NiAS samples exhibit distinctively higher catalytic activity in DRM with CO2 compared with their NiCS analogues. For the typical 3NiAS catalyst containing 3 mmol/g NiO, the conversions of CO2 and CH4 are 64.2% and 53.7% at 750 °C respectively, which are evidently higher than that of CO2 (40.7%) and CH4 (29.0%) over 3NiCS. Furthermore, the NiAS materials present good coking-resistance, while their NiCS counterparts suffer from serious coking.

Because of their diverse structure, high porosity, and tunable functionality, metal-organic frameworks (MOFs) are of great interest for diverse applications, including catalysis. However, the poor hydrostability of most reported MOFs hinders their catalytic applications seriously. In addition, the development of an effective method to improve the catalytic activity of MOFs is another challenge. Here, we report for the first time the development of a double-solvent strategy to fabricate MOFs inside silica nanopores. A typical MOF (MOF-5) and a mesoporous silica with two-dimensional hexagonal pore regularity (SBA-15) were first attempted. The double-solvent strategy is based on a hydrophobic solvent and a hydrophilic solution containing MOF precursors with a volume equal to or less than the pore volume of the support so that the MOF can be formed selectively in the channels of support. Our results show that upon confinement in silica nanopores the hydrostability of MOF-5 is apparently improved. The framework of MOF-5 is destroyed obviously in a humid environment for 15 min, but that confined in SBA-15 is well preserved after 8 h. Moreover, the catalytic activity of the composite MOF-5@SBA-15 is superior to that of pure MOF-5 regarding activity and reaction rate. Under the catalysis of MOF-5@SBA-15, the conversion of benzyl bromide in the Friedel-Crafts alkylation reaction can reach 100% at 80 °C for 3 h, which is much higher than that of pure MOF-5 (61%) and SBA-15 (0%). We also demonstrate that the double-solvent strategy can be successfully extended to other MOFs, such as HKUST-1 and ZIF-8. Our work might open up an avenue for the improvement of stability and performance of MOFs, which is highly expected for a variety of applications.

Noble-metal nanoparticles have attracted great attention because of their excellent catalytic activity. However, the activity of noble-metal nanoparticles is severely dependent on the size of the metal nanoparticles. Therefore, regulation of the nanoparticle size is of great importance. Herein we report an efficient strategy for the first time to regulate the size of platinum (Pt) nanoparticles in a typical mesoporous silica SBA-15 by using the confined spaces. The Pt-containing precursor is introduced to the confined spaces between the template and silica walls in as-prepared SBA-15 by grinding. Subsequent calcination allows template removal and precursor conversion in one step and avoids repeated calcination in conventional modification processes. This leads to the formation of Pt nanoparticles with smaller size, making Pt metal catalysts highly active. Hence, the catalytic activity of the oxidation of trace ethylene is very superior to that of those prepared by the conventional method. For a typical material, PtAS-5, containing 5.0 wt % Pt, the complete conversion of ethylene was achieved at 40 °C, which is lower than that on the catalyst PtCS-5 prepared by the conventional method (50 °C) as well as that on a series of catalysts reported previously.

Owing to their high physicochemical stability and low skeleton density, polymers are highly promising for capturing the greenhouse gas CO2. However, complicated monomers, expensive catalysts, and/or severe conditions are usually required for their synthesis, which makes the process costly, tedious, and hard to scale up. In this paper, a facile nucleophilic substitution reaction is developed to synthesize polymers from low-cost monomers, namely chloromethylbenzene and various diamines. Due to the appropriate reactivity of monomers, the polymerization takes place at a low temperature of about 60 °C in the absence of any catalysts. A series of polymers containing plentiful secondary amines are successfully fabricated; these secondary amines provide a proper adsorbate–adsorbent interaction from the viewpoints of selective capture of CO2 and energy-efficient regeneration of adsorbents. Moreover, the materials possess well-defined micropores with the dimension close to the size of adsorbate molecules and subseq...

Homogeneous dual-ligand zinc complex catalysts was developed for the synthesis of propylene carbonate (PC) through chemical fixation of CO2. It was found that among a number of various pK a N-donor ligands, the catalytic performance was enhanced dramatically and the corrosion of the reaction system was effectively inhibited when 1-methylimidazol (1MI) was used as the N-donor ligand, in which >90 % PC yield could be obtained under mild reaction conditions. The dual-ligand zinc complex catalysts were characterized by various spectroscopic techniques such as FT-IR and 1HNMR. X-ray crystallography showed that the Zn(II) atom was coordinated in tetrahedron geometry by three bromine atom, one 1MI nitrogen atom, and one crystallographically independent cation to give a 3D tetrahedron structure, which forms tetracoordinated complexes. The structure of the complex gives the reasons for the enhancement of the catalytic activity from the microscopic molecular structure point of an extremely long and therefore labile Zn–Br bond, the diversification of the bond angles, and the interplay between the steric hindrance, which have great influence on the interaction forces of Zn–Br.

Due to their synthetic diversification, low skeletal density, and high physicochemical stability, porous polymer networks (PPNs) are highly promising in a variety of applications such as carbon capture. Nevertheless, complicated monomers and/or expensive catalysts are normally utilized for their synthesis, which makes the process tedious, costly, and hard to scale up. In this study, a facile nucleophilic substitution reaction was designed to fabricate PPNs from low-cost monomers, namely chloromethyl benzene and ethylene diamine. A surfactant template was also used to direct the assembly, leading to the formation of PPN with enhanced porosity. It is fascinating that the polymerization reactions can occur at the low temperature of 63 °C in the absence of any catalyst. The obtained PPNs contain abundant secondary amines, which offer appropriate adsorbate–adsorbent interactions from the viewpoints of selective CO2 capture and energy-efficient regeneration of the adsorbents. Hence, these PPNs are highly active in selective adsorption of CO2, and unusually high CO2/N2 and CO2/CH4 selectivity was obtained. Moreover, the PPN adsorbents can be completely regenerated under mild conditions.

Metal–organic frameworks (MOFs) have attracted extensive attention due to their large surface area, diverse structures, and tuneable functionality. However, the poor hydrostability of most reported MOFs hinders their practical applications severely. In this paper, we report a strategy to modulate the properties of a typical MOF, namely MOF-5 [Zn4O(BDC)3; BDC = 1,4-benzenedicarboxylate] by hybridizing it with a natural clay (i.e. attapulgite), for the first time. A new kind of hybrid material resulting from the hybridization of the MOF and attapulgite was thus constructed. Our results showed that the hydrostability of the MOF was apparently improved due to the hybridization with attapulgite. The frameworks of MOF-5 were degraded seriously under the humid atmosphere, while the structure of the hybrid materials could be well preserved. We also demonstrated that the hybrid materials were highly active in the heterogeneous Friedel–Crafts alkylation reaction of benzyl bromide with toluene. The conversion of benzyl bromide reached ∼100% under the reaction conditions investigated. More importantly, the catalytic stability of the hybrid materials was significantly enhanced owing to the introduction of attapulgite. The activity could be well recovered with no detectable loss, and the conversion remained at ∼100% at the sixth run, which was apparently higher than that of MOF-5 (27.7% at the sixth run). The excellent hydrostability, catalytic activity, and reusability make the present materials highly promising for utilization as heterogeneous catalysts in practical applications.

A redox strategy was designed to generate strong basicity on mesoporous silica by using the redox interaction of a precursor with methanol vapor. The formation of strongly basic sites was realized at 400 °C, which breaks the tradition of thermally induced decomposition that usually requires much higher temperatures (>600 °C).

Correction for ‘Smart adsorbents with reversible photo-regulated molecular switches for selective adsorption and efficient regeneration’ by Jing Zhu et al., Chem. Commun., 2016, 52, 11531–11534.