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Amines in porous materials have been employed as active species for the selective CO2 adsorption from natural gas because of their target-specific interactions. Nevertheless, it is difficult to modulate such strong interactions to reach a high efficiency in the adsorption processes. Herein, we fabricated light-responsive adsorbents with tunable adsorbent–adsorbate interactions for CO2 capture. The adsorbents were synthesized by introducing primary and secondary amines into a mesoporous silica that had been grafted with azobenzene groups on the surfaces. The target-specific amine sites render the adsorbents significantly selective in the uptake of CO2 over CH4, and the azobenzene groups were used as light-responsive switches to influence the adsorbent–adsorbate interactions. The adsorbents can freely adsorb CO2 when the azobenzene groups are in the trans state. Ultraviolet-light irradiation makes the azobenzene groups transform to the cis configuration, which greatly hinders amines in the uptake of CO2. The caused difference of adsorption capacity can reach 34.9%. The alternative irradiation by ultraviolet- and visible-light can lead to a recyclable regulation on adsorption performance. The changes of the electrostatic potentials of amines are responsible for the light-induced regulation on adsorption.

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 polyhedra (MOPs) have emerged as versatile platforms for artificial models of biological systems due to their discrete structure and modular nature. However, the design and fabricatio...

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.

CuI-Functionalized materials show high potential in numerous applications such as adsorptive desulfurization. Nonetheless, the instability of CuI against oxidation limits its practical applications, and exposure of CuI to air can lead to the formation of CuII owing to the presence of oxygen and moisture. Herein, an unexpected way to stabilize CuI against oxidation was designed by constructing a superhydrophobic microenvironment in original hydrophilic metal–organic frameworks (MOFs) via polystyrene (PS) coating. A pre-polymerization strategy is developed to coat PS on the surface of CuI-functionalized MIL-101(Cr) (CuIM) rather than entering the pores (producing CuIM@PS), and the access of moisture to CuI is hindered, thus stabilizing CuI regardless of the existence of oxygen. CuI in CuIM@PS is stable in the air with a constant relative humidity of 75% for 200 days, while almost all CuI is converted to CuII in CuIM in only 14 days. The optimal CuIM@PS material after air exposure can adsorb 0.208 mmol g−1 of thiophene, which is much superior to that of CuIM (0.024 mmol g−1) despite the comparable adsorption capacity for unexposed materials. Moreover, the present CuIM@PS adsorbents exhibit excellent adsorption performance for water-containing model fuels.

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.

Due to the good controllability and high energy efficiency in adsorption processes, photoresponsive adsorbents are intriguing for CO2 capture. Nevertheless, most reported photoresponsive adsorbents are designed based on weak adsorption sites, regulating CO2 adsorption through structural change or steric hindrance. In addition, ultraviolet (UV) light is commonly involved in the regulation of adsorption capacity. Here we report for the first time the smart adsorbents for CO2 capture, which makes strong adsorption sites respond to visible (Vis) light. The adsorbents were fabricated by introducing primary amine and Dispersed Red 1 (DR1, a kind of push-pull azobenzene that responds to Vis light rapidly) units to mesoporous silica, which act as strong adsorption sites and triggers, respectively. The primary amine sites make the adsorbents highly selective in the adsorption of CO2 over CH4. Without light irradiation, azobenzene is in the form of trans configuration, which leads to decreased electrostatic potential of primary amines and subsequently, exposure of active sites and liberal adsorption of CO2. Upon Vis-light irradiation, cis isomers are formed, which results in increased electrostatic potential of primary amines and subsequently shelter of active sites. Even on such strong adsorption sites, the alteration of CO2 adsorption capacity can reach 40% for the adsorbent with and without Vis-light irradiation. Moreover, the trans/cis isomerization of DR1 units can be triggered reversibly by Vis light. The present smart system endows adsorbents with selective adsorption capacity and avoids the employment of UV light, which is unlikely to be achieved by conventional photoresponsive adsorbents.

Due to the nontoxicity, low cost, and versatility, CuO-functionalized materials have received much attention. Their performances are intensely dependent on the dispersion state of CuO. Herein we re...

The zeolite Cu(I)Y is promising for adsorptive removal of thiophenic sulfur compounds from transportation fuels. However, its application is seriously hindered by the instability of Cu(I), which is easily oxidized to Cu(II) even under atmospheric environment due to the coexistence of moisture and oxygen. Here, we report the adjustment of zeolite microenvironment from hydrophilic to superhydrophobic status by coating polydimethylsiloxane (yielding Cu(I)Y@P), which isolates moisture entering the pores and subsequently stabilizes Cu(I) despite the presence of oxygen. Cu(I) in Cu(I)Y@P is stable upon exposure to humid atmosphere for 6 months, while almost all Cu(I) is oxidized to Cu(II) in Cu(I)Y for only 2 weeks. The optimized Cu(I)Y@P material after moisture exposure can remove 532 μmol g−1 of thiophene and is much superior to Cu(I)Y (116 μmol g−1), regardless of similar uptakes for unexposed adsorbents. Remarkably, Cu(I)Y@P shows excellent adsorption capacity of desulfurization for water-containing model fuel., Zeolite Cu(I)Y is attractive for adsorptive removal of sulfur compounds from fuel, however practical application is limited by instability of Cu(I). Here the authors use a coating to achieve superhydrophobicity in the zeolite, leading to improved Cu(I) stability against oxidation and thiophene removal.

Achieving efficient adsorption and desorption processes by controllably tuning the properties of adsorbents at different technical stages is extremely attractive. However, it is difficult for traditional adsorbents to reach the target because of their fixed active sites. Herein, we report on the fabrication of a smart adsorbent, which was achieved by introducing photoresponsive azobenzene derivatives with cis/trans isomers to Ce-doped mesoporous silica. These photoresponsive groups serve as “molecular switches” by sheltering and exposing active sites, leading to efficient adsorption and desorption. Ce is also doped to provide additional active sites in order to enhance the adsorption performance. The results show that the cis isomers effectively shelter the active sites, leading to the selective adsorption of methylene blue (MB) over brilliant blue (BB), while the trans isomers completely expose the active sites, resulting in the convenient release of the adsorbates. Both selective adsorption and efficient desorption can be realized controllably by these smart adsorbents through photostimulation. Moreover, the performance of the obtained materials is well maintained after five cycles.

N-doped porous carbon-based materials (NPCMs) with hierarchical pore structures have been considered to be a suitable alternative to meet the ever-increasing demands for supercapacitors; however, the universally low yield of the NPCMs has restricted their practical applications. Herein, a series of NPCMs with hierarchical pore structures are synthesized with significantly increased yields through the carbonization of the copolymer made from 2,4,6-tris(chloromethyl)mesitylene and p-phenylenediamine. The development of the hierarchical pore structures and the N content of the NPCMs show opposite dependences on the increasing carbonization temperature. The NPCM exhibits the best capacitive ability only if the sufficiently developed hierarchical structures and moderate N content are achieved simultaneously. Therefore, NPCM-600 that is carbonized at 600 °C with an excellent yield of 53.6% (wt.), large specific surface area of 1778 m2 g−1, and N content of 4.13% (wt.) yields an ideal specific capacitance of 298 F g−1 at the current density of 1 A g−1 and a perfect cycling stability of the capacitance after 10,000 cycles at 10 A g−1. The yield of the NPCM-600 is considerably higher than those for many other recently reported NPCMs. NPCM-600 also shows better capacitance than those of the other reported NPCMs, such as NOPC-bis-CN-3 (167 F g−1) and CHCPB-K-600 (260 F g−1).

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.

Rice straw-derived cellulose (RSC) with purity of 92 wt.% was successfully extracted from rice straw by a novel and facile strategy, which integrated the C2H5OH/H2O autocatalytic process, dilute alkali treatment and H2O2 bleaching process. Influencing factors of the cellulose extraction were systematically examined, such as ethanol concentration, alkali concentration, H2O2 bleaching process and so on; the optimal extraction conditions of cellulose was determined. A series of rice straw-derived cellulose acetate (RSCA) with different degree of substitution (DS) were prepared by the acetylation reaction; the effects of Ac2O/cellulose ratio, reaction temperature and reaction time on the acetylation reaction were investigated. Results of FTIR and XRD analysis demonstrated that highly purified RSC and RSCA were prepared comparing with the commercial cellulose and cellulose acetate. Solubility analysis of RSCA with different DS indicated as-prepared RSCA with DS of 2.82 possessed the best solubleness, which was suitable for electrospinning. Moreover, the flexible RSCA fibrous membrane was easily fabricated by a facile electrospinning method. Our proposed method provided a strategy for realizing the high-value utilization of waste rice straw resource, as prepared RSC and RSCA can be used as chemical raw material, and electrospun RSCA fibrous membrane has various applications in medical materials, food packaging, water purification and so on.

MXenes, an emerging class of two-dimensional (2D) transition-metal carbide materials, have received increasing attention for their interesting physiochemical properties. For not only MXenes but also other 2D materials, delamination is a requisite step for the exploitation of their unique properties. In this work, a facile method for exfoliating Ti3C2Tx MXene to nanosheets of small size with the aid of poly(vinylpyrrolidone) (PVP) is designed, which has never been reported to our knowledge. Since both hydrophobic methylene groups and hydrophilic amide groups are provided with PVP, this method is applicable in a wide range of solvents, such as ethanol, water, and chloroform. Considering the charge detrapping and trapping behavior of 2D transition-metal materials in PVP dielectric, a memory device with the configuration of reduced graphene oxide (rGO)/Ti3C2Tx-PVP/Au is directly fabricated with these well-dispersed Ti3C2Tx-PVP composites by the solution process technique. Interestingly, the resultant device exhibits a typical bistable electrical switching, ultralow switching voltage (∼0.9 V), and a nonvolatile rewritable memory effect with the function of flash. This work might pave the way of using MXenes for future data storage, which is an indispensable field nowadays.

N-doped porous carbons (NPCs) are characterized by well-developed porosity and N-doped active sites, which makes them suitable for CO2 capture. However, their application in practice is obstructed by the relatively low N-doped content and unsatisfactory adsorption capacity. Herein, we report the synthesis of NPCs through the rational design of the precursor NUT-21 (NUT means Nanjing Tech University) with a record-high N content (up to 46.16%, wt). The NUT-21 was fabricated by the polymerization of two simple monomers of 2,4,6-tris(bromomethyl)mesitylene and 3,5-diamino-1,2,4-triazole with an unusually high N content of 70.67% (wt). With the carbonization of NUT-21 at different temperatures (500, 600, and 700 °C, respectively), a series of NPCs possessing various porosity and N contents are produced, successfully. For the NPC generated at 600 °C, the N content can reach 7.41% (wt), the surface area is 2208 m2/g, the micropore volume is 0.791 cm3/g, and the CO2 capacity is up to 8.3 mmol/g at 273 K and 1 bar, which is much higher than those of benchmarks including 13X zeolite (4.1 mmol/g) and activated carbon (2.8 mmol/g), and most carbon-based adsorbents reported till now. It was proved in our previous studies that the ultrahigh N content of the precursor was beneficial for both the formation of developed porosity and the generation of abundant N-doped sites, which can give rise to superior capacity and selectivity of CO2 capture. The NPCs obtained may offer to be highly promising candidates for CO2 separation from gas mixtures including natural gas and flue gas.

Because of their nontoxicity, economic applicability, and excellent performance on adsorptive desulfurization, the fabrication of Cu(I) sites onto porous supports has drawn much attention. However, high temperatures (usually ≥700 °C) are required for the formation of Cu(I) sites from Cu(II) species through the traditional autoreduction method, which is unworkable for thermolabile metal-organic frameworks (MOFs). Here, we report a strategy named vapor-induced reduction (VIR) to convert Cu(II) species to Cu(I) in MIL-101(Cr), in which ethanol is used as an environmentally benign reductant. The entire formation of Cu(I) from Cu(II) with more than 96% selectivity is allowed, at a relatively low temperature of 200 °C, and well-maintains the structure of the MOF. Moreover, the generated Cu(I) sites exhibit good performances in adsorption desulfurization with regard to both activity and reusability.

Because of their high stability, abundant porosity, and tailorable surface properties, N-doped porous carbons (NPCs) have played a crucial part in CO2 capture. Development of an efficient and low-cost method to fabricate NPCs remains a significant challenge. Herein, we report for the first time the preparation of NPCs through the rational design of the N-enriched polymer NUT-20-EDA (NUT, Nanjing Tech University; EDA, ethylenediamine) as the precursor. The NUT-20-EDA was obtained by polymerization of two simple monomers of mesitylene and formaldehyde dimethyl acetal, followed by post-synthetic ammonification. Through carbonization at temperatures ranging from 600 °C to 800 °C, NPCs with different porosity and N contents are fabricated, successfully. The reference porous carbons (rPCs) are also synthesized based on the polymer NUT-20 without post-synthetic ammonification. For the representative sample generated at 700 °C (NPC-700), the surface area is up to 1852 m2/g, which is much larger than its counterpart rPC-700 (1324 m2/g). Moreover, the CO2 uptake of NPC-700 (7.1 mmol/g at 0 °C and 1 bar) is higher than that of rPC-700 (5.9 mmol/g), and also superior to those of many benchmarks reported, including 13X zeolite (4.1 mmol/g) and activated carbon (2.8 mmol/g). Therefore, it is proved that, as a pore-foaming agent during the carbonization, the amino groups incorporated play a significant role in the formation of abundant porosity of the NPCs, which is one of the crucial factors for CO2 adsorption, and the N-species doped in NPCs can work as the CO2-philic sites to enhance the CO2 capture.

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.

Mesitylene, a representative heavy carbon by-product in the course of C1 chemical downstream processes, is proposed to be employed in this study, as the initial material to synthesize the porous carbons that have played a crucial part in the adsorptive carbon capture process but are generally made from natural carbon resources, instead of fed to the traditional refining process such as hydroprocessing. Based on molecular dynamics calculation, it is proved that once the mesitylene monomers are linked by the flexible methylene groups, the generated polymer can closely mimic the lignin macromolecular behaviors in terms of spatial configuration and atomic thermal motions, which gifts the great potential of the mesitylene-based polymer as applicable a precursor of porous carbon as the biomass-based material. The experimental facts further demonstrate that the porous carbons produced through the routine carbonization of the mesitylene-based polymer can possess desired textural peculiarities, in particular the finely developed micropores that give rise to perfect capacity and selectivity of CO2 capture, of which underlying mechanism is revealed by the first-principle calculation. The porous carbon generated at 700 °C can reach the CO2 capture capacity of 6.16 mmol g−1 at 0 °C and 1 bar, which is much higher than many benchmark materials reported, including some biomass-based porous carbons (2.8 mmol g−1, at 0 °C and 1 bar).

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.

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.

Mixed matrix membranes (MMMs) derived from metal-organic frameworks (MOFs) nanocrystals represent a promising alternative for overcoming the trade-off between permeability and selectivity derived from the pristine polymeric membrane. The selection of MOFs fillers are mainly focused on their diffusion-selectivity property for gas-pairs. However, the improvement of both gas-permeability and selectivity through addition of sorption-selective MOFs are rarely reported. Herein, the incorporation of CO2-philic KAUST-7 (also referred to as NbOFFIVE-1-Ni) nanocrystals makes the neat 6FDA-Durene polyimide membrane more permeable and more selective, surpassing the state-of-the-art 2008 Robeson upper bound for CO2/CH4. Nano-sized (~ 80 nm) KAUST-7 crystals with sharp particle size distribution were first fabricated through a co-solvent synthesis method. The explored gas transportation mechanism indicates that the improvement of CO2/CH4 selectivity on MMMs are attributed to the significant raise of the sorption-selectivity rather than the diffusion-selectivity. The favorable interfacial interaction between the imide groups of the 6FDA and the H of the pyrazine in the KAUST-7 enhances plasticization resistance of the neat polymer membrane. The developed MMMs exhibit a promising application in CO2 capture from natural- and bio-gas.

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.

Herein we present a rational design and fabrication of nitrogen-enriched hierarchical porous polymer networks by direct use of polyethylenimine (usually loaded on porous supports) as the building b...

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 ...

Metal–organic polyhedra (MOPs) have attracted considerable research interest due to their unique cavity structure and fascinating physicochemical properties. However, their poor hydrostability and low processability hinder their applications seriously. Here we report a polymerization strategy (self-polymerization or copolymerization with styrene) to crosslink discrete MOP molecules, through which hydrophilic MOPs become hydrophobic, thus enhancing their hydrostability obviously. The obtained polymers exhibit much better selective CO2 adsorption performance than bulk MOPs. Moreover, the processability of these materials is greatly improved and solid-state materials with different shapes (e.g. cylindrical, tapered, and cubic) can be produced through utilizing their easy-curing and molding properties.

Photoresponsive adsorbents for CO2 capture attract significant attention, because the variation of adsorption capacity can be tailored conveniently by light irradiation. However, all photoresponsive adsorbents reported until now capture CO2 via physical interaction (weak sites). Thus, the selectivity of CO2 over other gases like CH4 is low, and the variation of CO2 adsorption capacity originates from pure structural change via isomerization of photoresponsive units. Despite great challenges, photoresponsive adsorbents for CO2 capture based on chemical interaction (strong sites) are extremely desirable. Here, we report for the first time the construction of photoresponsive adsorbents with chemical adsorption sites for CO2. The control of adsorption capacity is based on the interplay between active amine sites {A, [3-(methylamine)propyl]trimethoxysilane} and photoresponsive azobenzene molecules [P, 4-(3-triethoxysilylpropyl-ureido)azobenzene]. Density functional theory (DFT) calculations reveal that the neg...

Nanoporous adsorbents are highly efficient in selectively capturing aromatic sulfur compounds such as thiophene, benzothiophene, dibenzothiophene, and 4,6-dimethyldibenzothiophene that are refractory to remove by traditional techniques from liquid hydrocarbon fuels. In the past decades, great progress has been made in design and fabrication of nanoporous adsorbents as well as the judicious strategies of promoting their performance for deep desulfurization. However to the best of our knowledge, a comprehensive review from this perspective has never been reported until now. Therefore, a review summarizing these nanoporous adsorbents and advanced strategies is highly anticipated. In this review, we provide an overview of the synthesis methods, improvement strategies, and prospective of the nanoporous adsorbents for applications with adsorptive desulfurization. The concerned materials cover most of the traditional and recently emerged nanoporous materials, and are introduced and basically grouped by material type. Each category is illustrated with some typical examples, and the fundamental principles on how to design and fabricate nanoporous adsorbents are highlighted. The adsorption mechanism is discussed in detail as well.

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).

A series of polyethylenimine (PEI)-linked microporous organic polymers were obtained using glycidyl methacrylate-polyethylenimine monomer (GMA-PEI) and different cross-linking agents. Because of well-defined micropores and CO2-philic plentiful secondary amines, porous organic polymers (POPs) demonstrate high CO2 uptake and excellent selectivity over other permanent gases, such as CH4 and N2. The adsorption capacity of POPs reaches 92 mg g–1 at 273 K and 1 bar, which is higher than that of recently reported polymers supported on various porous materials such as MCM-41 (33 mg g–1), alumina (50 mg g–1), and SBA-15 (60 mg g–1) under the analogous conditions. The high CO2/N2 and CO2/CH4 selectivity is observed and reaches 308 and 39, respectively. It is noteworthy that POPs can be entirely regenerated under mild conditions and no loss in activity is detected after four cycles. Notably, no side product is obtained during the fabrication of POPs. Thus, good adsorption capacity, high selectivity, and energy-savin...

Novel periodic mesoporous organosilicas (PMOs) as functional nanomaterials based on the skeleton of lysine were synthesised by the co-condensation of lysine-bridged organosilicane (Lys-BOS) and tetraethyl orthosilicate in acidic medium using P123 as template. Furthermore, a large content of Lys-BOS was incorporated into the silica framework. Amino acid organosilicane (Lys-BOS) was first prepared by the multi-step reaction between traditional orgnaosilicane [(3-aminopropyl) triethoxysilane] and carboxyl protected lysine. The small-angle X-ray diffraction and N2 adsorption–desorption isotherms indicate that these PMO materials still retain ordered mesostructure in the high molar concentration of Lys-BOS. Fourier-transform infrared spectroscopy confirms that lysine is incorporated in the framework of the PMO materials.

Cu+-containing materials have drawn much attention in various applications because they are versatile, nontoxic, and low-cost. However, the difficulty of selective reduction and the poor stability of Cu+ species are now pretty much the agendas. Here, controlled construction of supported Cu+ sites in MIL-100(Fe) was realized under mild conditions (200 °C, 5 h) via a vapor-reduction strategy (VRS). Remarkably, the yield of Cu+ reaches 100%, which is quite higher than the traditional high-temperature autoreduction method with a yield less than 50% even at 700 °C for 12 h. More importantly, during the treatment via VRS some Fe3+ in MIL-100(Fe) are reduced to Fe2+, which prevent the frequently happened oxidation of Cu+ due to the higher oxidation potential of Fe2+. These properties make Cu+/MIL-100(Fe) efficient in the capture of typical aromatic sulfur, benzothiophene, with regard to both adsorption capacity and stability. To our knowledge, the stabilization of Cu+ using the oxidation tendency of supports is ...

Novel periodic mesoporous organosilicas materials (PMOs) based on the flexible skeleton of aspartic acid were synthesized by the co-condensation of aspartic acid-bridged organosilane (Asp-BOSP) and tetraethyl orthosilicate (TEOS) in an acidic medium, using the Pluronic P123 surfactant as a template. Furthermore, a new amino acid organosilane was developed by the simple reaction between traditional organosilicone ((3-aminopropyl) trimethoxysilane) and aspartic acid. The small-angle XRD and N2 adsorption-desorption isotherms demonstrate that these PMOs materials possess ordered 2D hexagonal mesostructures in the region of low molar concentrations of Asp-BOSP (⩽10%). Analysis of FTIR and 29Si MAS solid-state NMR confirm that the aspartic acid is incorporated into the framework of the PMOs materials.

Selective adsorption by use of metal-organic frameworks (MOFs) is an effective method for purification of hydrocarbon fuels. In consideration that the adsorption processes proceed in liquid phases, separation and recycling of adsorbents should be greatly facilitated if MOFs were endowed with magnetism. In the present study, we reported for the first time a dry gel conversion (DGC) strategy to fabricate magnetically responsive MOFs as adsorbents for deep desulfurization and denitrogenation. The solvent is separated from the solid materials in the DGC strategy, and vapor is generated at elevated temperatures to induce the growth of MOFs around magnetic Fe3O4 nanoparticles. This strategy can greatly simplify the complicated procedures of the well-known layer-by-layer method and avoid the blockage of pores confronted by introducing magnetic Fe3O4 nanoparticles to the pores of MOFs. Our results show that the adsorbents are capable of efficiently removing aromatic sulfur and nitrogen compounds from model fuels, for example removing 0.62mmolg-1S and 0.89mmolg-1N of thiophene and indole, respectively. In addition, the adsorbents are facile to separate from liquid phases by use of an external field. After 6 cycles, the adsorbents still show a good adsorption capacity that is comparable to the fresh one.

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.

The aim of this study is to examine the effectiveness of Partial Least Squares Regression (PLSR) method in determing correlations between the aroma profiles and sensory characteristics of wines. A total of 45 volatile compounds in five different Chinese grape wines were identified and quantified by HS-SPME/GC-MS and 26 of them with OAV (odour activity value) ＞1. All aroma compounds with OAV＞1 were selected for evaluating the correlations between the aroma profiles and 12 sensory descriptors using PLSR and their ROC (Relative Odour Contribution). The results showed that ethyl decanoate, ethyl hexanoate, acetaldehyde, isoamyl acetate, hexanoic acid, 4-vinylguaiacol and geraniol were the major contributors to the desirable balanced aroma of muscat wine. Ethyl hexanoate, ethyl butyrate, isoamyl acetate, acetaldehyde, hexanoic acid, 3-methyl-1-butanol and octanoic acid were mainly responsible for the aroma of black beet wine and cabernet gernischt wine whereas ethyl tetradecanoate, neryl acetate and nerol were the particular aroma compounds in black beet wine and γ-butyrolactone, nerolidol and β-ionone were special aroma compounds in cabernet gernischt wine. Both PLSR and ROC are effective methods to demonstrate the correlations between the sensory characteristics of the analyzed wines and their aroma compositions.

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.

Elimination of aromatic sulfur and nitrogen compounds via selective adsorption is an effective method for the purification of transportation fuels to meet the increasingly stringent environmental requirements. Since the adsorption processes proceed in liquid phases, separation and recycling of adsorbents should be greatly facilitated if they were endowed with magnetism. In the present study, magnetically responsive core–shell microspheres, Fe3O4@C, which comprise a magnetite core and a carbon shell with a thickness adjustable from 47 to 97 nm, were fabricated for the adsorption of aromatic sulfur and nitrogen compounds. The carbon shell derived from the carbonization of a resorcinol–formaldehyde polymer possesses abundant porosity with a hierarchical structure, which is highly active in the capture of aromatic sulfur and nitrogen compounds despite the absence of any active metal sites such as Cu(I) and Ag(I). Our results show that the Fe3O4@C adsorbents with BET surface areas ranging from 227 to 264 m2 g–...

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.

Fabrication of bifunctional Cu(I)/Ce(IV) sites in mesoporous silica SBA-15 requires a series of complicated steps, including introduction of the Ce(III) precursor, calcination to generate Ce(IV), further introduction of the Cu(II) precursor, and repeated calcination to generate Cu(I). This traditional method has low efficiency and wastes energy. Here we provide a highly efficient, convenient and green strategy for the fabrication of bifunctional Cu(I)/Ce(IV) sites in mesoporous silica SBA-15, for the first time. The precursors CuCl2 and CeCl3 were simultaneously introduced into SBA-15. Based on a guests-redox strategy, both the reduction of CuCl2 to CuCl and the oxidation of CeCl3 to CeO2 could be realized in one calcination step. This strategy avoids the repeated modification process, and guarantees a high Cu(I) yield of ∼59% without generation of toxic gas. In addition, the resultant materials show excellent performance in gas separation of C2H4 from C2H6.

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.

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...

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.

Porous organic polymers (POPs), with dramatic textural properties and versatile uses, were traditionally fabricated by means of rigid covalent bonds or linkages on the basis of judiciously chosen monomers or reaction types. In this study, a new fabrication mechanism of POPs is proposed. For the first time, supramolecular interaction is discovered to be robust to maintain the rigid structures of POPs, even with some flexible or rotatable chemical bonds/linkages, on which a series of successfully fabricated POPs code-named PoBCs are based. Both the first-principle calculations and experimental facts confirm that, owing to π-π stacking and van der Waals’ force, a multi-helix structure can be self-assembled in the course of PoBCs polymer chain growth, which effectively inhibits bending and twisting of the polymer chains and the collapse of intrinsic pore structures. Therefore, the as-synthesized PoBC, especially the PoBC-16, with rigid supramolecular structures possesses satisfactory BET specific surface area (1170 m2 g−1) and fully developed porosity (1.08 cm3 g−1), efficiently contributing to both the selective CO2 capture, of which capacity reaches 67.2 cm3 g−1 at 0 °C and 1 bar, and good reusability, even competitive with many representative benchmark POPs that are based on rigid covalent linkages, for instance, that code-named APOP (BET specific surface area, 490 m2 g−1; CO2 adsorption capacity, 43.6 cm3 g−1 at 0 °C and 1 bar).

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.

Metal–organic frameworks (MOFs) show high potential in adsorptive removal of aromatic sulfur compounds; however, the crucial factors affecting the adsorption performances are scarcely clarified. In the present study, three classic aromatic sulfur compounds (i.e., thiophene, benzothiophene, and 4,6-dimethyldibenzothiophene) as well as five typical MOFs (i.e., MOF-5, HKUST-1, MIL-53(Fe), MIL-53(Cr), and MIL-101(Cr)) were selected for study. The adsorptive desulfurization performances of MOFs were investigated by using a fixed-bed adsorption system. In the case of thiophene, the adsorption capacity of MOFs decreases in the order MIL-53(Cr) > HKUST-1 > MOF-5 > MIL-53(Fe) > MIL-101(Cr). For the first time, the adsorbate–adsorbent interaction was examined in detail by using infrared spectra and temperature-programmed desorption. Such an interaction was demonstrated to be the most important factor affecting adsorption performance. When the molecular size of aromatic sulfur compounds is comparable to or smaller t...