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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.

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

A vast amount of energy can be extracted from the untapped low-grade heat from sources below 100 °C and the Gibbs free energy from salinity gradients. Therefore, a process for simultaneous and direct conversion of these energies into electricity using permselective membranes was developed in this study. These membranes screen charges of ion flux driven by the combined salinity and temperature gradients to achieve thermo-osmotic energy conversion. Increasing the charge density in the pore channels enhanced the permselectivity and ion conductance, leading to a larger osmotic voltage and current. A 14-fold increase in power density was achieved by adjusting the ionic site population of covalent organic framework (COF) membranes. The optimal COF membrane was operated under simulated estuary conditions at a temperature difference of 60 K, which yielded a power density of ≈231 W m

Titanium metal-organic frameworks (Ti-MOFs), as an appealing type of artificial photocatalysts, have shown great potentials in the field of solar energy conversion due to their well-studied photo-redox activity similar to TiO 2 and good optical responsiveness of linkers serving as the antenna to absorb visible-light. Although enormous efforts have been dedicated to developing Ti-MOFs with high photocatalytic activity, their solar energy conversion performances are still poor. Herein, a covalent-integrated strategy has been implemented to construct a series of multivariate Ti-MOF/COF hybrid materials, PdTCPP⸦PCN-415(NH 2 )/TpPa (composites 1, 2, and 3), featuring excellent visible-light utilization, suitable band gap, and high surface area for photocatalytic H 2 production. Notably, the resulting composites demonstrated remarkably enhanced visible-light-driven photocatalytic H 2 evolution performance, especially for the composite 2 with the maximum H 2 evolution rate of 13.98 mmol g -1 h -1 (turn-over frequency (TOF) = 227 h -1 ), which is much higher than the prototypical counterparts, PdTCPP⸦PCN-415(NH 2 ) (0.21 mmol g -1 h -1 ) and TpPa (6.51 mmol g -1 h -1 ). Our work thereby suggests a new approach to develop highly efficient photocatalysts for photocatalytic H 2 evolution reaction and beyond.

Guided by a second-sphere interaction strategy, we fabricated a Tb(III)-based metal-organic framework (MMCF-4) for turn-on sensing of methyl amine with ultra-low detection limit and high turn-on efficiency. MMCF-4 features lanthanide nodes shielded in a nonacoordinate geometry along with secondary coordination spheres that are densely populated with H-bond interacting sites. Nonradiative routes were inhibited by binding-induced rigidification of the ligand on the second coordination sphere, resulting in luminescence amplification. Such remote interacting mechanism involved in the turn-on sensing event was confirmed by single-crystal X-ray diffraction and molecular dynamic simulation studies. The design of both primary and secondary coordination spheres of Tb(III) enabled the first turn-on sensing of organic amines in aqueous conditions. Our work suggests a promising strategy for high-performance turn-on sensing for Ln-MOFs and luminous materials driven by other metal chromophores.

Herein, various robust, crystalline, and porous organic frameworks based on in-situ-formed imine-linked oligomers were investigated; these oligomers self-assembled through collaborative intermolecular hydrogen bonding interactions via liquid-liquid interfacial reactions. The soluble oligomers were kinetic products with multiple unreacted aldehyde groups that acted as hydrogen bond donors and acceptors and directed the assembly of the resulting oligomers into three-dimensional frameworks. The sequential formation of robust covalent linkages and highly reversible hydrogen bonds enforced long-range symmetry and facilitated the production of large single crystals, with structures that were unambiguously determined and refined based on high-quality single-crystal X-ray diffraction data. Impressively, the unique hierarchical arrangements increased the steric hindrance of the imine bond, which prevented attacks from water molecules, thereby greatly improving the stability. Furthermore, the multiple binding sites in the resultant frameworks enabled the rapid sequestration of micropollutant in water.

Adsorption-based cooling is an energy-efficient renewable-energy technology that can be driven using low-grade industrial waste heat and/or solar heat. Here, we report the first exploration of fluorocarbon adsorption using porous covalent organic polymers (COPs) for this cooling application. High fluorocarbon R134a equilibrium capacities and unique overall linear-shaped isotherms are revealed for the materials, namely COP-2 and COP-3. The key role of mesoporous defects on this unusual adsorption behavior was demonstrated by molecular simulations based on atomistic defect-containing models built for both porous COPs. Analysis of simulated R134a adsorption isotherms for various defect-containing atomistic models of the COPs shows a direct correlation between higher fluorocarbon adsorption capacities and increasing pore volumes induced by defects. Combined with their high porosities, excellent reversibility, fast kinetics, and large operating window, these defect-containing porous COPs are promising for adsorption-based cooling applications.

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 C

Attributed to the unique topological complexity and elegant beauty, Borromean systems are attracting intense attention. However, at present, the construction of Borromean linked organic polymers remains a challenge. To address this formidable challenge, we developed a supramolecular-synthon-driven approach to fabricate Borromean linked organic polymer. The solvothermal condensation reaction of a judiciously selected trigonal pyramidal building block, 1,3,5-Tris(4-aminophenyl)adamantane, with linear dialdehyde building blocks allowed the construction of two rare covalent organic frameworks (COFs) with high crystallinity and robustness. Structure refinement unveiled the successful formation of entangled 2D→2D Borromean arrayed structures. Both the two COFs were of microporosity and thus demonstrated the potentials for gas separation. The successful synthesis of the first two Borromean linked organic polymers paves the avenue to expand the supramolecular-synthon-driven approach to other building blocks and topologies, and broadens the family and scope of COFs.

To offset the environmental impact of platinum-group element (PGE) mining, recycling techniques are being explored. Porous organic polymers (POPs) have shown significant promise owing to their selectivity and ability to withstand harsh conditions. A series of pyridine-based POP nanotraps, POP-Py, POP-pNH2 -Py, and POP-oNH2 -Py, have been designed and systematically explored for the capture of palladium, one of the most utilized PGEs. All of the POP nanotraps demonstrated record uptakes and rapid capture, with the amino group shown to be vital in improving performance. Further testing on the POP nanotrap regeneration and selectivity found that POP-oNH2 -Py outperformed POP-pNH2 -Py. Single-crystal X-ray analysis indicated that POP-oNH2 -Py provided a stronger complex compared to POP-pNH2 -Py owing to the intramolecular hydrogen bonding between the amino group and coordinated chlorine molecules. These results demonstrate how slight modifications to adsorbents can maximize their performance.

peer-reviewed Developing new materials for the fabrication of proton exchange membranes (PEMs) for fuel cells is of great significance. Herein, a series of highly crystalline, porous, and stable new covalent organic frameworks (COFs) have been developed by a stepwise synthesis strategy. The synthesized COFs exhibit high hydrophilicity and excellent stability in strong acid or base (e.g., 12 m NaOH or HCl) and boiling water. These features make them ideal platforms for proton conduction applications. Upon loading with H3PO4, the COFs (H3PO4@COFs) realize an ultrahigh proton conductivity of 1.13×10−1 S cm−1, the highest among all COF materials, and maintain high proton conductivity across a wide relative humidity (40–100 %) and temperature range (20–80 °C). Furthermore, membrane electrode assemblies were fabricated using H3PO4@COFs as the solid electrolyte membrane for proton exchange resulting in a maximum power density of 81 mW cm−2 and a maximum current density of 456 mA cm−2, which exceeds all previously reported COF materials.

The removal of C

peer-reviewed Herein, we report that a new flexible coordination network, NiL2 (L=4‐(4‐pyridyl)‐biphenyl‐4‐carboxylic acid), with diamondoid topology switches between non‐porous (closed) and several porous (open) phases at specific CO2 and CH4 pressures. These phases are manifested by multi‐step low‐pressure isotherms for CO2 or a single‐step high‐pressure isotherm for CH4. The potential methane working capacity of NiL2 approaches that of compressed natural gas but at much lower pressures. The guest‐induced phase transitions of NiL2 were studied by single‐crystal XRD, in situ variable pressure powder XRD, synchrotron powder XRD, pressure‐gradient differential scanning calorimetry (P‐DSC), and molecular modeling. The detailed structural information provides insight into the extreme flexibility of NiL2. Specifically, the extended linker ligand, L, undergoes ligand contortion and interactions between interpenetrated networks or sorbate–sorbent interactions enable the observed switching.

A major driving force behind the recent surge of interest in metal–organic frameworks (MOFs) lies with their amenability to design using crystal engineering strategies. In particular, MOFs with specific composition and topology can be targeted by judicious selection of organic linkers and metal-based molecular building blocks (MBBs) that serve as nodes. Furthermore, their modular nature means that prototypal MOFs can serve as blueprints or platforms for a plethora of derivatives with controlled pore size and surface area, as exemplified by the practice of “reticular synthesis”. Such features make MOFs stand out over traditional porous materials, and afford them with potential for use in gas storage, separation, CO2 capture, [6] sensor, catalysis, and other areas. High-symmetry MOFs based upon high-connectivity polyhedral cage MBBs that are in effect supermolecular building blocks (SBBs) can provide exquisite control over structure because of their high connectivity and also afford the features of confined nanospace and extra-large surface area. Such MOFs have afforded superior performance in the context of gas storage for hydrogen, methane, CO2, and other gas molecules. 11,12] The nature of the nanospace in SBB-based MOFs is such that they can encapsulate catalytically active species, for example, organometallics, polyoxometallates, metalloporphyrins (porph@MOMs), and enzymes. Along with encapsulation of catalysts, it is possible to generate porphyrin-walled MOFs by customdesigning metalloporphyrin moieties so that they can serve as vertices and/or edges and/or faces. In principle, the metal clusters residing on the vertices could also contribute as active sites to achieve an even higher density of active sites than that of porph@MOMs. Polyhedral MOFs are therefore attractive targets as catalyst supports for heterogeneous catalysis. However, although metallosalens and metalloporphyrins have been utilized as linkers for catalytically active MOFs and polyhedral cage-containing metal–metalloporphyrin frameworks exist, MOFs sustained by catalytically active metalloporphyrin linkers and catalytically active MBBs remain unexplored. Herein, we report such a MOF that based upon a previously reported fcu topology net built from 12-connected cubohemioctahedral SBBs of formula [Co2(m2-H2O)(H2O)4]6(bdc)12 and benzoimidephenanthroline tetracarboxylate (bipa-tc) linkers (Scheme 1a), fcu-MOF-1. The new com

Porous metal–organic frameworks (MOFs), which have emerged as new zeolite analogues, have attracted considerable research interest in the past decade as, compared to traditional zeolites, they possess a high surface area, modifiable surface, and tunable pore size. These characteristics have led to an enormous application potential for MOFs in catalysis, gas storage, and adsorptive separation. One of the main concerns regarding porous MOFs is their limited thermal stability, which prevents them from competing with inorganic zeolites in practical applications. Most porous MOFs can only be heated up to 150–350 8C without losing their framework integrity. Interpenetration, which often arises from weak interactions, has been widely used to improve the thermal stability of porous MOFs, and interpenetrated porous MOFs that are stable up to 400 8C have been reported. Interpenetration increases the wall thickness and reduces the pore size of an MOF, both of which lead to enhanced thermal stability. If two interpenetrated frameworks can be linked through coordinative bonds, the thermal stability should be boosted still further (Scheme 1). Herein we report such a coordinatively linked, doubly interpenetrated Yb MOF with improved thermal stability (up to 500 8C) and uncommon gas-adsorption selectivity. We have previously reported a cobalt-based porous MOF with doubly interpenetrated, (8,3)-connected nets (PCN-9; PCN: porous coordination network). PCN-9 contains a square-planar Co4(m4-O) secondary building unit (SBU) where each Co center is five-coordinate with a coordination site open toward the channel. As a consequence of this interpenetration, PCN-9 is thermally stable up to 400 8C (by thermogravimetric analysis (TGA)). If the interpenetrated, (8,3)-connected nets can be linked at the open metal sites by a bridging ligand, the thermal stability of the resulting MOF should be still higher. A short bridge is the best candidate due to the proximity of the two nets, and we chose SO4 2 as the bridging ligand because it can chelate the two metal centers and stabilize the MOF further. In addition, it can be generated slowly under solvothermal conditions through decomposition of DMSO (dimethyl sulfoxide), thereby facilitating the formation of the coordinatively linked interpenetrated MOF. Initial attempts to use sulfates to bridge the doubly interpenetrated, (8,3)-connected nets in PCN-9 failed. There are two possible reasons for this failure: the limited coordination number (maximum of six) of the cobalt center and the need for additional counterions to balance the overall charge. The coordination number of the metal center can be increased by using Ln cations instead of Co and no additional counterions will be needed in this case to balance the overall charge. With these considerations in mind, a ytterbium MOF with coordinatively linked, doubly interpenetrated, (8,3)-connected nets (PCN-17) was synthesized. Studies of similar MOFs containing other lanthanides are currently underway and will be reported in due course elsewhere. PCN-17 is stable up to 480 8C and exhibits selective adsorption of H2 and O2 over N2 and CO. Crystals of PCN-17 were obtained upon heating a mixture of H3TATB (TATB= 4,4’,4’’-S-triazine-2,4,6-triyl tribenzoate) and ytterbium nitrate in DMSO at 145 8C for 72 hours. The formula of PCN-17 (Yb4(m4-H2O)(C24H12N3O6)8/3(SO4)2·3H2O·10DMSO) was determined by X-ray crystallography, elemental analysis, and thermogravimetric analysis (TGA). X-ray structural analysis revealed that PCN-17 crystallizes in the space group Im3m. As expected, it adopts a square-planar Yb4(m4H2O) SBU, with the m4-H2O molecule, which is probably disordered over two or more orientations (see below), residing at the center of a square of four Yb atoms (Figure 1a). The four Yb atoms in the SBU lie in the same plane and each coordinates to seven O atoms (four from four carboxylate groups of four different TATBs, two from the bridging sulfate generated in situ, and one from the m4H2O). The Yb···m4-H2O distance (2.70 D) indicates very weak Scheme 1. a) A single net. b) Two doubly interpenetrated nets. c) Interpenetrated nets linked by a coordinative bond. The vertical gold dotted line represents a p–p interaction; the blue solid line represents coordinative bonding.