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Hierarchically porous metal-organic frameworks (HP-MOFs), dominating both the micro- and mesoporous regimes, show high potentials in various applications especially those involving bulky biomolecules. The templating method has been proven to be effective in the fabrication of HP-MOFs; however, complicated synthetic systems containing solvents, templates, and additives are frequently employed. Here we report the first example of designing a poly(ethylene glycol)-based alkylammonium and bromide multifunctional ionic liquid (IL) as a solitary medium to construct HP-MOFs, avoiding the involvement of any additional media. Besides the ready solubilization of MOF precursors in the multifunctional IL due to a poly(ethylene glycol) chain as the solubilizer, the ionic moiety facilitates electrostatic interaction to create a templating effect. Hence, UiO-66 with hierarchical porosity has been successfully fabricated, and such a methodology can also be applied to the construction of other HP-MOFs. The resultant HP-UiO-66 is efficient in the encapsulation of bulky biomolecule cytochrome c, and the adsorption capacity is obviously superior to that of the microporous counterpart.

Adsorptive separation plays a critical role in chemical, food, pharmaceutical, and environmental industries, as well as in many other industrial areas. Adsorbents are most important for adsorptive separation and undergo adsorption and desorption processes to accomplish the specific tasks of separation. In the process of adsorption, adsorbates diffuse into the pore spaces of adsorbents through pore openings, adsorb on active sites via physical or chemical interactions, and subsequently are regenerated by temperature or pressure swings during desorption. In the process of adsorption and desorption, however, the requirements for pore structures and surface properties of adsorbents are different. In general, adsorbents with small pore openings can realize selective adsorption and do not favor desorption; on the other hand, adsorbents with large pore openings are efficient in desorption but at the expense of adsorption selectivity. Remarkably, active sites possessing strong interactions with adsorbates contribute to high selectivity for adsorption, while desorption becomes difficult. The trade-off between adsorption and desorption presents an enormous challenge to develop high-efficiency adsorbents. Restricted by their fixed structures and surface properties, conventional adsorbents are unable to meet the demands of adsorption and desorption processes simultaneously.To confront the obstacles, the development of advanced adsorbents to meet the demand of adsorptive separation are urgent. A key strategy to address such issues lies in dynamically adjusting the pore structures or the surface properties of adsorbents with controllability according to the demands of adsorption/desorption. For instance, pursuant to the requirements of varying pore structures during adsorption/desorption, the pore openings of adsorbents can be customized through dynamic structural change of the decorated stimuli-sensitive motifs by suitable external intervention. In addition, the active sites within the adsorbents can be exposed to enhance the adsorption selectivity or sheltered to accelerate the desorption through stimuli-triggered adsorbent-adsorbate interactions. Hence, we proposed a concept of process-oriented smart adsorbents (POSAs) on the basis of the requirements of the adsorption/desorption processes. The design and development of such POSAs are based on three aspects, namely, pore openings, pore spaces, and adsorption sites of adsorbents.In this Account, we present the progress in the development of POSAs according to the demands of adsorption/desorption processes. A series of POSAs with incorporated stimuli-sensitive motifs were successfully achieved. The versatility of incorporated motifs allows them to tune the pore structures and surface properties of adsorbents dynamically and further to enhance the adsorption and desorption efficiency simultaneously. Based on the concept of POSAs, we hope that this Account could contribute to the development of high-efficiency adsorbents and ultimately promote their applications in practical industrial separation. Moreover, we present an outlook on future trends and challenges on the road toward the development and applications of POSAs.

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.

Light-responsive metal–organic frameworks (LMOFs) are intriguing materials for CO2 capture owing to their tunable structures and performances. However, conventional LMOFs are reported to regulate C...

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

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...

Layer-structured MoO3 with a high theoretical specific capacity is a promising lithium-ion battery (LIB) anode alternative material. However, the poor electrical conductivity and pulverization duri...

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...

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.

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 sufficient surface areas, developed porosities, and high stabilities, N-doped porous carbons (NDPCs) have presented an excellent CO2 adsorption ability. NDPCs are usually fabricated through the carbonization of N-containing polymers. The effect of N species enlarging surface areas and foaming pores has been confirmed. However, traditional polymer precursors of NDPCs must have a relatively high N content and give unsatisfactory structural characters and CO2 capacities of their NDPCs. In this study, an NDPC precursor code-named NUT-50-EDA with a N content of only 6.4 wt % is prepared, while the amino groups in the precursor still play a significant role in the porogen during the carbonization process. The generated NDPCs show more abundant micropores, larger surface areas, and higher CO2 adsorption capacities compared to those of the counterpart porous carbons (PCs) made from the precursor without ammonification. With a relatively low N content (1.5 wt %), NDPC-700 with a large surface area...

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.

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...

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...

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 ...

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...

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...