Porous materials with open metal sites have been investigated to separate various gas mixtures. However, open metal sites show the limitation in the separation of some challenging gas mixtures, such ...as C2H2/CO2. Herein, we propose a new type of ultra‐strong C2H2 nano‐trap based on multiple binding interactions to efficiently capture C2H2 molecules and separate C2H2/CO2 mixture. The ultra‐strong acetylene nano‐trap shows a benchmark Qst of 79.1 kJ mol−1 for C2H2, a record high pure C2H2 uptake of 2.54 mmol g−1 at 1×10−2 bar, and the highest C2H2/CO2 selectivity (53.6), making it as a new benchmark material for the capture of C2H2 and the separation of C2H2/CO2. The locations of C2H2 molecules within the MOF‐based nanotrap have been visualized by the in situ single‐crystal X‐ray diffraction studies, which also identify the multiple binding sites accountable for the strong interactions with C2H2.
A new type of ultra‐strong C2H2 nano‐trap featuring the synergistic effect of multiple open metal sites has been proposed for separating C2H2/CO2 mixture gas. The unique C2H2 nano‐trap shows the strongest binding interaction with C2H2 and a benchmark for C2H2/CO2 separation. The binding mechanism for C2H2 was studied through single‐crystal X‐ray diffraction experiments and molecular simulation studies.
Industrial synthesis is driven by a delicate balance of the value of the product against the cost of production. Catalysts are often employed to ensure product turnover is economically favorable by ...ensuring energy use is minimized. One method, which is gaining attention, involves cooperative catalytic systems. By inserting a flexible polymer into a metal–organic framework (MOF) host, the advantages of both components work synergistically to create a composite that efficiently fixes carbon dioxide to transform various epoxides into cyclic carbonates. The resulting material retains high yields under mild conditions with full reusability. By quantitatively studying the kinetic rates, the activation energy was calculated, for a physical mixture of the catalyst components to be about 50 % higher than that of the composite. Through the unification of two catalytically active components, a new opportunity opens up for the development of synergistic systems in multiple applications.
More than the sum of its parts: Two catalytically active components, a metal–organic framework (MOF) host and an ionic polymer, are combined into a single material. They synergistically work together lowering the energy barrier of a reaction, further than a mixture of the individual components. This process is demonstrated by the fixation of carbon dioxide with epoxides, forming industrially relevant cyclic carbonates.
Herein, we show how the spatial environment in the functional pores of covalent organic frameworks (COFs) can be manipulated in order to exert control in catalysis. The underlying mechanism of this ...strategy relies on the placement of linear polymers in the pore channels that are anchored with catalytic species, analogous to outer‐sphere residue cooperativity within the active sites of enzymes. This approach benefits from the flexibility and enriched concentration of the functional moieties on the linear polymers, enabling the desired reaction environment in close proximity to the active sites, thereby impacting the reaction outcomes. Specifically, in the representative dehydration of fructose to produce 5‐hydroxymethylfurfural, dramatic activity and selectivity improvements have been achieved for the active center of sulfonic acid groups in COFs after encapsulation of polymeric solvent analogues 1‐methyl‐2‐pyrrolidinone and ionic liquid.
Creating a solvation environment: The catalytic performance of sulfonic acid groups in covalent organic frameworks (COFs) can be greatly amplified by the introduction of polymeric solvent analogues, which create desired solvation environments through hydrogen‐bonding interactions. Improved activity and selectivity was demonstrated by the COF‐catalyzed dehydration of fructose to produce 5‐hydroxymethylfurfural.
Climate change, caused by heavy CO2 emissions, is driving new demands to alleviate the rising concentration of atmospheric CO2 levels. Enlightened by the photosynthesis of green plants, ...photo(electro)chemical catalysis of CO2 reduction, also known as artificial photosynthesis, is emerged as a promising candidate to address these demands and is widely investigated during the past decade. Among various artificial photosynthetic systems, solar‐driven electrochemical CO2 reduction is widely recognized to possess high efficiencies and potentials for practical application. The efficient and selective electroreduction of CO2 is the key to the overall solar‐to‐chemical efficiency of artificial photosynthesis. Recent studies show that various metallic materials possess the capability to play as electrocatalysts for CO2 reduction. In order to achieve high selectivity for CO2 reduction products, various efforts are made including studies on electrolytes, crystal facets, oxide‐derived catalysts, electronic and geometric structures, nanostructures, and mesoscale phenomena. In this Review, these methods for tuning the selectivity of CO2 electrochemical reduction of metallic catalysts are summarized. The challenges and perspectives in this field are also discussed.
Different approaches for tuning the selectivity of CO2 electrochemical reduction on metallic catalysts are summarized, including studies in electrolytes, crystal facets, oxide‐derived catalysts, electronic and geometric structures, nanostructures, and mesoscale phenomena. The challenges and perspectives for future practical CO2 electroreduction and utilization in this field are also discussed.
Herein, a dynamic spacer installation (DSI) strategy has been implemented to construct a series of multifunctional metal—organic frameworks (MOFs), LIFM‐61/31/62/63, with optimized pore space and ...pore environment for ethane/ethylene separation. In this respect, a series of linear dicarboxylic acids were deliberately installed in the prototype MOF, LIFM‐28, leading to a dramatically increased pore volume (from 0.41 to 0.82 cm3 g−1) and reduced pore size (from 11.1×11.1 Å2 to 5.6×5.6 Å2). The increased pore volume endows the multifunctional MOFs with much higher ethane adsorption capacity, especially for LIFM‐63 (4.8 mmol g−1), representing nearly three times as much ethane as the prototypical counterpart (1.7 mmol g−1) at 273 K and 1 bar. Meanwhile, the reduced pore size imparts enhanced ethane/ethylene selectivity of the multifunctional MOFs. Theoretical calculations and dynamic breakthrough experiments confirm that the DSI is a promising approach for the rational design of multifunctional MOFs for this challenging task.
A dynamic spacer installation (DSI) strategy has been developed to realize a series of multifunctional metal—organic frameworks (MOFs) with optimized pore space and pore environment for ethane/ethylene separation. The installation of functional spacers into the proto‐LIFM‐28 not only improves the pore volume, but also reduces the pore size, leading to enhanced C2H6/C2H4 separation performance.
Asymmetric hydrogenation, a seminal strategy for the synthesis of chiral molecules, remains largely unmet in terms of activation by non‐metal sites of heterogeneous catalysts. Herein, as demonstrated ...by combined computational and experimental studies, we present a general strategy for integrating rationally designed molecular chiral frustrated Lewis pair (CFLP) with porous metal–organic framework (MOF) to construct the catalyst CFLP@MOF that can efficiently promote the asymmetric hydrogenation in a heterogeneous manner, which for the first time extends the concept of chiral frustrated Lewis pair from homogeneous system to heterogeneous catalysis. Significantly, the developed CFLP@MOF, inherits the merits of both homogeneous and heterogeneous catalysts, with high activity/enantio‐selectivity and excellent recyclability/regenerability. Our work not only advances CFLP@MOF as a new platform for heterogeneous asymmetric hydrogenation, but also opens a new avenue for the design and preparation of advanced catalysts for asymmetric catalysis.
A highly active heterogeneous chiral frustrated Lewis pair system has been achieved for the first time via incorporating rationally designed bifunctional chiral FLP molecules into a MOF under the guidance of computational studies; the afforded CFLP@MOF demonstrated superb catalysis performances in heterogeneous asymmetric hydrogenation with excellent recyclability/regenerability.
Visible light-induced photocatalysis is a promising way for environmental remediation due to efficient utilization of solar energy. Recently, metal-organic frameworks (MOFs) have attracted increasing ...attention in the field of photocatalysis. In comparison with traditional metal oxide semiconductors, MOFs have many advantages, such as high specific surface area, rich topology and easily tunable porous structure. In this review, we aim to summarize and illustrate recent advances in MOF-based photocatalysis for environmental remediation under visible light, including wastewater treatment, air purification and disinfection. A series of strategies have been designed to modify and regulate pristine MOFs for enhanced photocatalytic performance, such as ligand functionalization, mixed-metal/linker strategy, metal ion/ligand immobilization, dye sensitization, metal nanoparticle loading, carbon material decoration, semiconductor coupling, MOF/COF coupling, carrier loading and magnetic recycling. The above modifications may result in extended visible light absorption, efficient generation, separation and transfer of photogenerated charges, as well as good recyclability. However, there are still many challenges and obstacles. In order to meet the requirements of using MOF photocatalysis as a friendly and stable technology for low-cost practical applications, its future development prospects are also discussed.
Highly photoactive MOFs can be engineered
via
various strategies for the purpose of extended visible light absorption, more efficient generation, separation and transfer of charge carriers, as well as good recyclability.
The capture of the xenon and krypton from nuclear reprocessing off‐gas is essential to the treatment of radioactive waste. Although various porous materials have been employed to capture Xe and Kr, ...the development of high‐performance adsorbents capable of trapping Xe/Kr at very low partial pressure as in the nuclear reprocessing off‐gas conditions remains challenging. Herein, we report a self‐adjusting metal‐organic framework based on multiple weak binding interactions to capture trace Xe and Kr from the nuclear reprocessing off‐gas. The self‐adjusting behavior of ATC‐Cu and its mechanism have been visualized by the in‐situ single‐crystal X‐ray diffraction studies and theoretical calculations. The self‐adjusting behavior endows ATC‐Cu unprecedented uptake capacities of 2.65 and 0.52 mmol g−1 for Xe and Kr respectively at 0.1 bar and 298 K, as well as the record Xe capture capability from the nuclear reprocessing off‐gas. Our work not only provides a benchmark Xe adsorbent but proposes a new route to construct smart materials for efficient separations.
A self‐adjusting metal–organic framework has been proposed for capturing trace Xe and Kr from the nuclear reprocessing off‐gas. The self‐adjusting behavior endows ATC‐Cu the highest Xe and Kr capacity at 0.1 bar and 298 K, as well as a benchmark for capturing low concentration Xe and Kr. The mechanism of the self‐adjusting behavior has been studied through single‐crystal X‐ray diffraction experiments and computational calculations.
Exponential growth in the field of covalent–organic frameworks (COFs) is emanating from the direct correlation between designing principles and desired properties. The comparison of catalytic ...activity between single‐pore and dual‐pore COFs is of importance to establish structure–function relationship. Herein, the synthesis of imine‐linked dual‐pore (BPyDC)x%‐ETTA COFs (x = 0%, 25%, 50%, 75%, 100%) with controllable bipyridine content is fulfilled by three‐component condensation of 4,4′,4″,4′″‐(ethene‐1,1,2,2‐tetrayl)tetraaniline (ETTA), 4,4′‐biphenyldialdehyde, and 2,2′‐bipyridyl‐5,5′‐dialdehyde in different stoichiometric ratio. The strong coordination of bipyridine moieties of (BPyDC)x%‐ETTA COFs with palladium imparts efficient catalytic active sites for selective functionalization of sp2 CH bond to CX (X = Br, Cl) or CO bonds in good yield. To broaden the scope of regioselective CH functionalization, a wide range of electronically and sterically substituted substrates under optimized catalytic condition are investigated. A comparison of the catalytic activity of palladium decorated dual‐pore frameworks with single‐pore imine‐linked Pd(II) @ Py‐2,2′‐BPyDC framework is undertaken. The finding of this work provides a sporadic example of chelation‐assisted CH functionalization and disclosed an in‐depth comparison of the relationship between superior catalytic activity and core properties of rationally designed imine linked frameworks.
Metal‐catalyzed functionalization of sp2 and sp3 carbonhydrogen bond is very appealing for pharmaceutical industry. Immobilization of palladium is critical to optimize the catalytic activity of covalent organic frameworks with recyclability and reusability. This article illustrates the structure–functional relationship of palladium decorated dual‐pore and single‐pore covalent–organic frameworks through regioselective carbonhydrogen to carbonchlorine, carbonbromine, and carbonoxygen functionalization.
Connecting molecular building blocks by covalent bonds to form extended crystalline structures has caused a sharp upsurge in the field of porous materials, especially covalent organic frameworks ...(COFs), thereby translating the accuracy, precision, and versatility of covalent chemistry from discrete molecules to two-dimensional and three-dimensional crystalline structures. COFs are crystalline porous frameworks prepared by a bottom-up approach from predesigned symmetric units with well-defined structural properties such as a high surface area, distinct pores, cavities, channels, thermal and chemical stability, structural flexibility and functional design. Due to the tedious and sometimes impossible introduction of certain functionalities into COFs
via de novo
synthesis, pore surface engineering through judicious functionalization with a range of substituents under ambient or harsh conditions using the principle of coordination chemistry, chemical conversion, and building block exchange is of profound importance. In this review, we aim to summarize dynamic covalent chemistry and framework linkage in the context of design features, different methods and perspectives of pore surface engineering along with their versatile roles in a plethora of applications such as biomedical, gas storage and separation, catalysis, sensing, energy storage and environmental remediation.
This review article summarizes the recent progress in the pore surface engineering of covalent organic frameworks (COFs) for various applications.
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