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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.

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.

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.

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.

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.

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).

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.

To date, some attempts have been made to synthesize hierarchically porous metal-organic frameworks (HPMOFs), and in most cases, mesopores are formed in microporous frameworks. However, mass transfer and diffusion are still limited in such HPMOFs since micropores connect mesopores and mesopores are noncontinuous. Here, we fabricate a new hierarchical structure through the formation of microporous MOFs within continuous mesoporous channels. Confined space in the as-prepared mesoporous silica-containing template was used to prepare well-dispersed metal precursor of ZnO. The strategy of ligand vapor-induced crystallization was then designed to construct MOFs inside mesoporous channels, in which vapored ligand at elevated temperature diffuses and reacts with metal precursor. Our results indicate that framework isomerism is controllable by adjusting the crystallization conditions. In comparison to their microporous and mesoporous counterparts, the hierarchically porous materials show obviously enhanced adsorption performance on a series of bulky molecules including dye, enzyme, and metal-organic polyhedron.

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.

The use of porous carbons for selective CO2 separation attracts increasing attention. Owing to low thermostability of porous polymers, low yield is the major concern of porous carbons. To obtain po...

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.

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.

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.

Here, we designed a double-solvent/host-guest redox combined strategy to construct Cu+ sites in metal-organic frameworks (MOFs) for the first time. As a proof of concept, a representative MOF MIL-100(Fe) with tunable valence states of cations was employed as the host. The combined strategy realizes selective introduction of Cu2+ precursors to the interior pores of MIL-100(Fe), remarkably minimizing the aggregation of Cu2+ and subsequently formed Cu+ species. Owing to the proper reducibility of in situ formed Fe2+ in the frameworks, controlled conversation of Cu2+ to Cu+ with ∼100% yield is achieved in the absence of any additional reducing agents. These characteristics make the obtained materials Cu+-modified MIL-100(Fe) highly active in selective CO adsorption. The CO adsorption capacity is up to 3.75 mmol·g-1 at 298 K and 1 bar, which is superior to all other Cu+-containing adsorbents reported so far such as CuCl/activated carbon (2.5 mmol·g-1), CuCl/γ-Al2O3 (1.0 mmol·g-1), and CuCl/SBA-15 (0.50 mmol·g-1). The same adsorbent also exhibits quite high selectivity of CO over N2, and the ideal adsorption solution theory selectivity reaches 424. The outstanding CO adsorption performance make the present adsorbents great potential in separation of CO from various mixtures.

Selective adsorption of CO2 from natural gas results in increased calorific value, decreased gas volume, and reduced corrosion. For this purpose, the development of high-performance adsorbents with regard to both adsorption capacity and CO2/CH4 selectivity receives great attention. Herein, two new conjugated microporous polymers (CMPs) were prepared by Yamamoto homocoupling and Sonogashira–Hagihara cross-coupling reaction. The significant role of homo- and cross-coupling in CMPs in selective CO2 separation was investigated. Notably, the cross-coupled CMP (NUT-15, NUT means Nanjing Tech University) shows CO2 uptake around twice that of homocoupled CMP (NUT-14) under the analogous conditions. Furthermore, the importance of KOH-activation and temperature-controlled carbonization in efficient CO2 capture was studied. For this, NUT-15 was further subjected to carbonization and highly active porous carbons (PCs) were obtained. It is noteworthy that PC-800 with high carbonization yield (78%) and suitable pore st...

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.

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...

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...

Owing to the rigid standards of manufacturing semiconductor components, decrease of the moisture to parts-per-billion (ppb), at a global level, is always vital but extremely nerve-racking in the production of high-purity gases. Herein, typical adsorbents including oxides (SiO2 and γ-Al2O3), zeolites (4A and NaX), and metal–organic frameworks (MOFs; HKUST-1, UiO-66, and ZIF-8) are investigated with respect to the abilities of ultradeep dewatering from N2. Compared with other adsorbents, NaX performs much better on both dewatering efficiency (DE, from 2750 to 66 ppb) and the adsorption capacity (AC, 1.55 × 104 L N2·g–1). Moreover, it is for the first time experimentally and theoretically proved that the dewatering ability of X zeolite mainly depends on its cation species (Na+, Li+, K+, Cs+, Mg2+, Ca2+, Sr2+, or Ba2+), the forces between the zeolite and H2O, and the number of H2O molecules per cell of the zeolite. CaX thus shows a fascinating DE from 2750 to 33 ppb, a huge AC of 9.08 × 104 L N2·g–1, and an i...

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).

Cu(I)-containing materials have great potential in various applications such as in CO adsorption; however, development of an efficient and controllable method to produce Cu(I) sites remains a significant challenge; herein, a two-step double-solvent (DS) strategy is reported for the first time to fabricate Cu(I) sites in a representative metal–organic framework, MIL-101(Cr); this strategy ensures that both introduction of the Cu(II) precursor and its reduction to Cu(I) occur inside the pores and significantly minimizes the aggregation of Cu species. This is difficult to realize through conventional methods used for Cu(II) introduction (wet impregnation) or reduction (liquid-phase reduction). The two-step DS strategy involves selective reduction of Cu(II) to form Cu(I) without the formation of any Cu(0). The obtained Cu(I)-containing materials exhibit an excellent CO adsorption capacity (up to 2.42 mmol g−1) at 298 K and 1 bar, much better than that of the benchmark adsorbents including CuCl/γ-Al2O3 (1.0 mmol g−1), CuCl/MCM-41 (0.57 mmol g−1), and CuZSM-5 (0.11 mmol g−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.

New amino-acid-bridged periodic mesoporous organosilicas (PMOs) were constructed by hydrolysis and condensation reactions under acid conditions in the presence of a template. The tyrosine bissilylated organic precursor (TBOS) was first prepared through a multistep reaction by using tyrosine (a natural amino acid) as the starting material. PMOs with the tyrosine framework (Tyr-PMOs) were constructed by simultaneously using TBOS and tetraethoxysilane as complex silicon sources in the condensation process. All the Tyr-PMOs materials were characterized by XRD, FTIR spectroscopy, N2 adsorption-desorption, TEM, SEM, and solid-state 29 Si NMR spectroscopy to confirm the structure. The horseradish peroxidase (HRP) enzyme was first immobilized on these new Tyr-PMOs materials. Optimal conditions for enzyme adsorption included a temperature of 40 °C, a time of 8 h, and a pH value of 7. Furthermore, the novel Tyr-PMOs materials could store HRP for approximately 40 days and maintained the enzymatic activity, and the Tyr-PMOs-10 % HRP with the best immobilization effect could be reused at least eight times.

It is highly desired to develop a new strategy for the regeneration of metal–organic frameworks (MOFs) adsorbents as the complete release of ethane from MOFs needs a larger energy input via traditional techniques. Herein, we explored the desorption of ethane from a photothermal MOF composite (T/Zr-PDI) with high efficiency via light-triggered remote heating. Under the irradiation of near-infrared (NIR) light, the derived radical anions from T/Zr-PDI can convert NIR light into thermal energy and the temperature of the whole adsorbent can be quickly elevated to 87 °C in several minutes owing to its high photothermal conversion efficiency. Under the optimal conditions, 100% desorption of ethane can be realized. Different from the traditional desorption techniques, light-triggered remote heating only heats the adsorbent via irradiating the photothermal PDI parts, further transferring to the surroundings. In this project, the PDIs as “nanoheaters” are homogeneously distributed which is beneficial to solve the heat insulation problem of MOFs. This current light-triggered desorption strategy might provide a solution for the development of a new type of effective desorption system.

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 ...

Presently, chemical Si/Al sources are predominantly used as raw materials for the synthesis of zeolites in spite of their high cost. Here, we report for the first time the direct synthesis of a ZSM-5 zeolite by using a natural clay, attapulgite (ATP), as the low-cost and environmentally benign Si/Al source through a vapor-induced transformation (VIT) method, in which the vapor diffuses into ATP and interacts with the framework. In a crystallization recipe, ATP is well present with a pristine crystal structure, and the yield of zeolite reaches 96%. The resultant zeolite exhibits well-defined crystallinity and porosity, which are comparable to the counterpart synthesized from traditional chemical Si/Al sources. In the synthetic process, the formation of Si–F species plays an important role, which promotes the transformation of an ATP crystal to a zeolite crystal. Meanwhile, the metal elements (e.g., Al, Fe, and Mg) of ATP exist in the zeolite products, and at least part of them are located in the zeolite fr...

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.

Selective adsorption and energy-saving regeneration are two important issues for adsorptive separation. However, it is impossible for traditional adsorbents with changeless pore properties to realize both of them. In this study, a strategy was proposed to design and fabricate a new generation of adsorbents via grafting the thermoresponsive polymers (TPs), namely, poly(N-isopropylacrymide) (PNIPAM), onto the pore surface of mesoporous silica SBA-15. The TPs disperse homogeneously in pore space and act as molecular switches which are reversibly closed or opened with the change of temperature. At the temperature of adsorption below the lower critical solution temperature (LCST), TPs are extended as a result of their extensive hydrogen bonding interactions with water and the molecular switches are closed. It is easier for smaller adsorbates to enter than larger ones, and the selective adsorption can be consequently realized. At the temperature of desorption (above LCST), TPs shrink owing to their hydrogen bon...

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.

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.

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.

Owing to their high physicochemical stability, low skeletal density, tailorable surface properties, and high porosity, microporous crosslink polymers are highly promising for selective CO2 capture, separation, and storage. The crosslinking (CL) and crosslinker length (CLL) in a polymer play a quite significant role in enhancing selective CO2 capture. To investigate the role of CL and CLL, polymers with no crosslinking (non-crosslinking, NCL), and small-(SCL), and long-crosslinker lengths (LCL) were successfully fabricated. It is noteworthy that the polymer containing SCL has remarkable CO2 adsorption capacity and selectivity over the polymer with LCL and NCL. High selectivity for CO2 over CH4/N2 was observed in the sequence SCL > LCL > NCL. This indicates that not only CL but CLL is also significantly important in generating highly efficient adsorbents. The adsorption capacity reaches 208.3 mg g−1, which is higher than that of the benchmarks including activated carbon (122.8 mg g−1), and 13X zeolite (180.3 mg g−1), as well as most reported carbon-based adsorbents. The CO2/N2 and CO2/CH4 selectivity reaches 541.4 and 64, respectively. Moreover, excellent recyclability was observed without loss in CO2 adsorption for 10 cycles. Thus, high CO2 capture, excellent selectivity, and high recyclability under energy-saving mild regeneration conditions make microporous polymers a unique adsorbent for selective CO2 capture from flue gas and natural gas.

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.