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The removal of carbon dioxide (CO2) from acetylene (C2H2) is a critical industrial process for manufacturing high-purity C2H2. However, it remains challenging to address the tradeoff between adsorption capacity and selectivity, on account of their similar physical properties and molecular sizes. To overcome this difficulty, here we report a novel strategy involving the regulation of a hydrogen-bonding nanotrap on the pore surface to promote the separation of C2H2/CO2 mixtures in three isostructural metal-organic frameworks (MOFs, named MIL-160, CAU-10H, and CAU-23, respectively). Among them, MIL-160, which has abundant hydrogen-bonding acceptors as nanotraps, can selectively capture acetylene molecules and demonstrates an ultrahigh C2H2 storage capacity (191 cm3 g-1, or 213 cm3 cm-3) but much less CO2 uptake (90 cm3 g-1) under ambient conditions. The C2H2 adsorption amount of MIL-160 is remarkably higher than those for the other two isostructural MOFs (86 and 119 cm3 g-1 for CAU-10H and CAU-23, respectively) under the same conditions. More importantly, both simulation and experimental breakthrough results show that MIL-160 sets a new benchmark for equimolar C2H2/CO2 separation in terms of the separation potential (Δqbreak = 5.02 mol/kg) and C2H2 productivity (6.8 mol/kg). In addition, in situ FT-IR experiments and computational modeling further reveal that the unique host-guest multiple hydrogen-bonding interaction between the nanotrap and C2H2 is the key factor for achieving the extraordinary acetylene storage capacity and superior C2H2/CO2 selectivity. This work provides a novel and powerful approach to address the tradeoff of this extremely challenging gas separation.

Biomimetic metal-organic frameworks have attracted great attention as they can be used as bio-inspired models, allowing us to gain important insights into how large biological molecules function as catalysts. In this work, we report the synthesis and utilization of such a metal-metalloporphyrin framework (MMPF) that is constructed from a custom-designed ligand as an efficient halogen bond donor catalyst for Diels-Alder reactions under ambient conditions. The implementation of fabricated halogen bonding capsule as binding pocket with high-density C-Br bonds enabled the use of halogen bonding to facilitate organic transformations in their three-dimensional cavities. Through combined experimental and computational studies, we showed that the substrate molecules diffuse through the pores of the MMPF, establishing a host-guest system via the C-Br⋅⋅⋅π interaction. The formation of halogen bonds is a plausible explanation for the observed boosted catalytic efficiency in Diels-Alder reactions. Moreover, the unique capability of MMPF highlights new opportunities in using artificial non-covalent binding pockets as highly tunable and selective catalytic materials.

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.

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.

Metallocorrole macrocycles that represent a burgeoning class of attractive metal-complexes from the porphyrinoid family, have attracted great interest in recent years owing to their unique structure and excellent performance revealed in many fields, yet further functionalization through incorporating these motifs into porous nanomaterials employing the bottom-up approach is still scarce and remains synthetically challenging. Here, we report the targeted synthesis of porous organic polymers (POPs) constructed from custom-designed Mn and Fe-corrole complex building units, respectively denoted as CorPOP-1(Mn) and CorPOP-1(FeCl). Specifically, the robust CorPOP-1(Mn) bearing Mn-corrole active centers displays superior heterogeneous catalytic activity toward solvent-free cycloaddition of carbon dioxide (CO2) with epoxides to form cyclic carbonates under mild reaction conditions as compared with the homogeneous counterpart. CorPOP-1(Mn) can be easily recycled and does not show significant loss of reactivity after seven successive cycles. This work highlights the potential of metallocorrole-based porous solid catalysts for targeting CO2 transformations, and would provide a guide for the task-specific development of more corrole-based multifunctional materials for extended applications.

An In(III) based metal-organic framework (MOF), In-pbpta, with soc topology was constructed from the trigonal prismatic [In3(μ3-O)(H2O)3(O2C-)6] secondary building unit (SBU) and a custom-designed tetratopic linker H4pbpta (pbpta = 4,4',4″,4‴-(1,4-phenylenbis(pyridine-4,2,6-triyl))-tetrabenzoic acid)). The obtained MOF shows a Brunauer-Emmett-Teller surface area of 1341 m2/g with a pore volume of 0.64 cm3/g, which is the highest among the scarcely reported In-soc-MOFs. The constructed MOF demonstrates excellent performance as a heterogeneous Lewis acid catalyst for highly efficient conversion in a one-pot multicomponent Strecker reaction for the preparation of α-aminonitriles under solvent-free conditions, which can be easy to separate and recycle without significant loss of activity for up to seven cycles. The computational modeling studies suggest the presence of the three substrates in close vicinity to the In-oxo cluster. The strong interactions of the aldehyde/ketone and the amine with the In-oxo cluster together with the readily available cyanide ion around the In-oxo cluster lead to high catalytic conversion within a short period of time for the MOF catalyst. Our work therefore lays a foundation to develop MOF as a new class of efficient heterogeneous catalyst for one-pot Strecker reaction.

It has long been a challenge to fabricate angstrom-sized functional pores for mimicking the function of biological channels to afford selective transmembrane transport. In this study, we describe a facile strategy to incorporate ionic elements into angstrom-sized channels using de novo encapsulation of charged dye molecules during the interface polymerization of a three-dimensional covalent organic framework (3D COF). We demonstrate that this approach is tailorable as it enables control over both the type and content of the guest and thus allows manipulation of the membrane function. The resulting membranes exhibit excellent permselectivity and low membrane resistance, thereby indicating the potential for harvesting salinity gradient (blue) energy. As a proof-of-concept study, the reverse electrodialysis device coupled with positive and negative dye encapsulated COF membranes afforded a power density of up to 51.4 W m-2 by mixing the simulated seawater and river water, which far exceeds the commercialization benchmark (5 W m-2). We envision that this strategy will pave the way for constructing new multifunctional biomimetic systems.

Understanding the origin of the catalytic activity for the development of efficient catalysts is critical yet challenging. Herein, we report a simple strategy for the synthesis of chromium nitride ...

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 C2 H2 /CO2 . Herein, we propose a new type of ultra-strong C2 H2 nano-trap based on multiple binding interactions to efficiently capture C2 H2 molecules and separate C2 H2 /CO2 mixture. The ultra-strong acetylene nano-trap shows a benchmark Qst of 79.1 kJ mol-1 for C2 H2 , a record high pure C2 H2 uptake of 2.54 mmol g-1 at 1×10-2 bar, and the highest C2 H2 /CO2 selectivity (53.6), making it as a new benchmark material for the capture of C2 H2 and the separation of C2 H2 /CO2 . The locations of C2 H2 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 C2 H2 .

Developing photocatalysts capable of visible-light-driven water splitting to produce clean hydrogen (H2) is one of the premier challenges for solar energy conversion into clean and sustainable fuel...

In this issue of Chem Catalysis, Yang and co-workers describe the preparation of enzyme@metal-organic framework composites for efficient biocatalysis under both weakly acidic and basic conditions. This work unambiguously provides a general and green co-precipitation method of orderly immobilizing enzymes in metal-organic frameworks, which will be instructive for research in both academia and industry.

Multifunctional catalysts derived from the integration of discrete catalytic partners in a confined space represent an important approach to emulate some of the design philosophies of enzymes. In an effort to design concepts for highly active catalysts for CO2 transformations, we synthesize and contrast the performance of two porous pyridinium frameworks. The activity is found to be significantly amplified by the introduction of the amine group on the ortho position of the pyridinium moieties. The resulting catalyst is capable of highly active and selective cycloaddition of aziridines with CO2 to 5-substituted-2-oxazolidinone, even under ambient conditions (1 bar, 22 °C). Its high activity originates from CO2 activation by the pendant amine group in the vicinity of the active species, which facilitates the subsequent catalytic steps.

An enzyme formulation using customized enzyme activators (metal ions) to directly construct metal-organic frameworks (MOFs) as enzyme protective carriers is presented. These MOF carriers can also serve as the disintegrating agents to simultaneously release enzymes and their activators during biocatalysis with boosted activities. This highly efficient enzyme preparation combines enzyme immobilization (enhanced stability, easy operation) and homogeneous biocatalysis (fast diffusion, high activity). The MOF serves as an ion pump that continuously provides metal ion activators that greatly promote the enzymatic activities (up to 251 %). This MOF-enzyme composite demonstrated an excellent protective effect against various perturbation environments. A mechanistic investigation revealed that the spontaneous activator/enzyme release and ion pumping enable enzymes to sufficiently interact with their activators owing to the proximity effects, leading to a boost in biocatalytic performance.

Herein, for the first time, we present the successful synthesis of a novel two-dimensional corrole-based covalent organic framework (COF) by reacting the unusual approximately T-shaped 5,10,15-tris(p-aminophenyl)corrole H3 TPAPC with terephthalaldehyde, which adopts desymmetrized hcb topology and consists of a staggered AB stacking structure with elliptical pores. The resultant corrole-based COF, TPAPC-COF, exhibits high crystallinity and excellent chemical stability. The combination of extended π-conjugated backbone and interlayer noncovalent π-π interactions endows TPAPC-COF with excellent absorption capability in the entire visible-light and even near-infrared regions. Moreover, this work suggests the promise of TPAPC-COF as a new class of photoactive material for efficient singlet-oxygen generation with potential photodynamic therapy application as demonstrated by in vitro anticancer studies.

Summary There has been a surge of interest in light-driven chemical transformations using organic photoredox catalysts, whereby a suitable energy alignment and efficient exciton migration are crucial for achieving high efficiency. We show here that covalent organic frameworks (COFs) offer the flexibility required to be ideal platforms for photocatalyst design, lending themselves to fine control over photoreactivity. To understand the factors that dictate photoreactivity, we explore a comparative study of a series of porous materials built with amine bonds with varied composition, crystallinity, and topology, in the efficiency of photogenerated reactive oxygen species. Combined spectroscopies, density functional theory calculations, and catalytic evaluations revealed an essential interplay among these parameters and the photoreactivity of the resulting materials. Beyond basic considerations, such as spectral absorption and crystallinity, the material's lattice symmetry has a significant impact on photoreactivity. We anticipate that the structure-performance relationships developed will provide a robust rule of thumb for designing COF-based photocatalysts.

The development of highly efficient and robust biomimetic catalysts is an essential and feasible strategy to overcome the intrinsic drawbacks of natural enzymes. Inspired by the synthetic strategy of covalent organic frameworks, we adopted a covalent-bond-driven strategy to prepare polyoxometalate (POM) based open frameworks (NKPOM-OFs = Nankai University POM-OFs) with abundant Mo[double bond, length as m-dash]O groups that can mimic the active center of sulfite oxidase. Four 2-dimensional (2D) NKPOM-OFs were designed and synthesized via the condensation reaction of linear amino-containing POMs with planar tetra-aldehyde monomers. Benefitting from the high crystallinity, the structures of 2D POM-OFs can be successfully determined from structural simulations. The results unveiled that NKPOM-OFs possessed 2D staggered stacking layered structures with the sql topology. All these NKPOM-OFs exhibited high crystallinity and stability and demonstrated outstanding performance to serve as biomimetic catalysts of sulfite oxidase with good recyclability. Notably, exfoliation of NKPOM-OFs under ultrasonic treatment can significantly boost the catalytic activity with almost two times faster reaction rates. This study not only enriches the facile and versatile synthesis strategy for POM-OFs but also provides new biomimetic platforms for biocatalysis.

Optimizing interfacial contacts and thus electron transfer phenomena in heterogeneous electrocatalysts is an effective approach for enhancing electrocatalytic performance. Herein, we successfully synthesized ultrafine β-Mo2C nanoparticles confined within hollow capsules of nitrogen-doped porous carbon (β-Mo2C@NPCC) and found that the surface layer of molybdenum atoms was further oxidized to a single Mo–O surface layer, thus producing intimate O–Mo–C interfaces. An arsenal of complementary technologies, including XPS, atomic-resolution HAADF-STEM, and XAS analysis clearly reveals the existence of O–Mo–C interfaces for these surface-engineered ultrafine nanostructures. The β-Mo2C@NPCC electrocatalyst exhibited excellent electrocatalytic activity for the hydrogen evolution reaction (HER) in water. Theoretical studies indicate that the highly accessible ultrathin O–Mo–C interfaces serving as the active sites are crucial to the HER performance and underpinned the outstanding electrocatalytic performance of β-Mo2C@NPCC. This proof-of-concept study opens a new avenue for the fabrication of highly efficient catalysts for HER and other applications, whilst further demonstrating the importance of exposed interfaces and interfacial contacts in efficient electrocatalysis.

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

The structural advantages of metal-organic frameworks (MOFs) can facilitate wide applications in the field of catalysis, including oxidation, hydrogenation, acetalization, transesterification, catalytic cracking, and so on. The efficiency of catalysis is closely related to the synergy between active center, auxiliary center, and microenvironment. Researchers can customize MOFs according to the needs of catalytic reactions, and many strategies were established for boosting catalytic performance. In this review, we aim to summarize and illustrate recent progress in the nanospace engineering of MOFs. Generally, MOFs were engineered mainly from the following aspects: 1) Regulation of pore size, including micropores, mesopores, and macropores. 2) Engineering of encapsulated active species, such as metal nanoparticles, quantum dots, polyoxometalates, enzymes, etc. 3) Engineering of MOFs morphology from zero dimension to three-dimension. 4) Controllable integration of MOFs with multi-strategies. 5) Construction of multivariate MOFs via introducing multiple or mixed organic functional groups into the existing framework. Besides, for further low cost and practical applications, challenges for MOFs as green and sustainable catalysts are also discussed.

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.

Metal–organic frameworks (MOFs) have shown promising potential for biomimetic functionality due to their tailorable metal-containing nodes and organic ligands. Several important structural parallels exist between metalloenzymes and the well defined geometric structure of MOFs. This emerging class of materials exhibits notable structural analogies to the active sites in metalloenzymes constructed by coordinating ligands and metals with similar binding patterns. More importantly, biomimetic MOFs can exhibit significant enhancements in terms of stability, cost-efficiency and a controllable microenvironment over traditional metalloenzymes, which make biomimetic MOFs attractive for broader industrial applications. MOF-based biomimetic catalysis is still rudimentary, but it has been investigated corresponding to both the principles of designing biomimetic MOFs and their potential applications. Herein, we depict the progress of MOF-based biomimetic catalysts, covering the versatile synthetic strategies and subsequent catalytic performance, alongside an investigation of the structural parallels between enzymes and biomimetic MOFs via the replication of enzymatically active sites and microenvironments.

The corrole unit from the porphyrinoid family represents one of the most important ligands in the field of coordination chemistry, which creates a unique environment allowing for the observation of unusual electronic states of bound metal cations and has shown great promise in various applications. Nevertheless, studies that directly and systematically introduce these motifs in porous crystalline materials for targeting further functionalizations are still lacking. Herein, we report for the first time the construction of two robust corrole-based metal-organic frameworks (MOFs), M6(μ3-O)4(μ3-OH)4(OH)3(H2O)3(H3TCPC)3 (M = Zr for Corrole-MOF-1 and M = Hf for Corrole-MOF-2, H3TCPC = 5,10,15-tris(p-carboxylphenyl)corrole), which are assembled by a custom-designed C2ν-symmetric corrolic tricarboxylate ligand and the unprecedented D3d-symmetric 9-connected Zr6/Hf6 clusters. The resultant frameworks feature a rare (3,9)-connected gfy net and exhibit high chemical stability in aqueous solutions within a wide range of pH values. Furthermore, we successfully prepared the cationic Corrole-MOF-1(Fe) from the iron corrole ligand, which can serve as an efficient heterogeneous catalyst for [4 + 2] hetero-Diels-Alder reactions between unactivated aldehydes and a simple diene, outperforming both the homogeneous counterpart and the porphyrinic MOF counterpart.

We herein develop a two-in-one molecular design strategy for facile synthesis of 2D imine based covalent organic frameworks (COFs). The integration of two different functional groups (i.e., formyl and amino groups) in one simple pyrene molecule affords a bifunctional building block: 1,6-bis(4-formylphenyl)-3,8-bis(4-aminophenyl)pyrene (BFBAPy). Highly crystalline and porous Py-COFs can be easily prepared by the self-condensation of BFBAPy in various solvents, such as CH

Precise control of the outer-sphere environment around the active sites of heterogeneous catalysts to modulate the catalytic outcomes has long been a challenge. Here, we demonstrate how this can be fulfilled by encapsulating catalytic components into supramolecular capsules, used as building blocks for materials synthesis, whereby the microenvironment of each active site is tuned by the assembled wall. Specifically, using a cationic template equipped with a polymerizable functionality, anionic ligands can be encapsulated by ion pair-directed supramolecular assembly, followed by construction into porous frameworks. The hydrophilic ionic wall enables reactions to be achieved in water that usually requires organic solvents and also facilitates the enrichment of the substrate into the hydrophobic pocket, leading to superior catalytic performances as demonstrated by the industrially relevant hydroformylation. Remarkably, the formation of the supramolecular assembly and catalyst encapsulation further engenders reaction selectivity, which reaches an even greater extent after construction of the porous framework., Tuning the environment of catalytic active sites may improve the selectivity of heterogeneous catalysts. Here, the authors modify the outer-sphere environment of active sites in hydroformylation catalysts by encapsulating the active sites in nanovessels formed by ion pair-directed supramolecular assembly.

Atomically dispersed metal catalysts anchored on nitrogen-doped (N-doped) carbons demand attention due to their superior catalytic activity relative to that of metal nanoparticle catalysts in energy storage and conversion processes. Herein, we introduce a simple and versatile strategy for the synthesis of hollow N-doped carbon capsules that contain one or more atomically dispersed metals (denoted as H-M-Nx-C and H-Mmix-Nx-C, respectively, where M = Fe, Co, or Ni). This method utilizes the pyrolysis of nanostructured core-shell precursors produced by coating a zeolitic imidazolate framework core with a metal-tannic acid (M-TA) coordination polymer shell (containing up to three different metal cations). Pyrolysis of these core-shell precursors affords hollow N-doped carbon capsules containing monometal sites (e.g., Fe-Nx, CoNx, or Ni-Nx) or multimetal sites (Fe/Co-Nx, Fe/Ni-Nx, Co/Ni-Nx, or Fe/Co/Ni-Nx). This inventory allowed exploration of the relationship between catalyst composition and electrochemical activity for the oxygen reduction reaction (ORR) in acidic solution. H-Fe-Nx-C, H-Co-Nx-C, H-FeCo-Nx-C, H-FeNi-Nx-C, and H-FeCoNi-Nx-C were particularly efficient ORR catalysts in acidic solution. Furthermore, the H-Fe-Nx-C catalyst exhibited outstanding initial performance when applied as a cathode material in a proton exchange membrane fuel cell. The synthetic methodology introduced here thus provides a convenient route for developing next-generation catalysts based on earth-abundant components.

As a major greenhouse gas, methane, which is directly vented from the coal-mine to the atmosphere, has not yet drawn sufficient attention. To address this problem, we report a methane nano-trap that features oppositely adjacent open metal sites and dense alkyl groups in a metal-organic framework (MOF). The alkyl MOF-based methane nano-trap exhibits a record-high methane uptake and CH4 /N2 selectivity at 298 K and 1 bar. The methane molecules trapped within the alkyl MOF were crystalographically identified by single-crystal X-ray diffraction experiments, which in combination with molecular simulation studies unveiled the methane adsorption mechanism within the MOF-based nano-trap. The IAST calculations and the breakthrough experiments revealed that the alkyl MOF-based methane nano-trap is a new benchmark for CH4 /N2 separation, thereby providing a new perspective for capturing methane from coal-mine methane to recover fuel and reduce greenhouse gas emissions.

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.

Frustrated Lewis pairs (FLPs) have recently been advanced as efficient metal-free catalysts for catalytic hydrogenation, but their performance in chemoselective hydrogenation, particularly in heterogeneous systems, has not yet been achieved. Herein, we demonstrate that, via tailoring the pore environment within metal-organic frameworks (MOFs), FLPs not only can be stabilized but also can develop interesting performance in the chemoselective hydrogenation of α,β-unsaturated organic compounds, which cannot be achieved with FLPs in a homogeneous system. Using hydrogen gas under moderate pressure, the FLP anchored within a MOF that features open metal sites and hydroxy groups on the pore walls can serve as a highly efficient heterogeneous catalyst to selectively reduce the imine bond in α,β-unsaturated imine substrates to afford unsaturated amine compounds.

Photomechanical molecular crystals are receiving much attention due to their efficient conversion of light into mechanical work and advantages including faster response time; higher Young's modulus; and ordered structure, as measured by single-crystal X-ray diffraction. Recently, various photomechanical crystals with different motions (contraction, expansion, bending, fragmentation, hopping, curling, and twisting) are appearing at the forefront of smart materials research. The photomechanical motions of these single crystals during irradiation are triggered by solid-state photochemical reactions and accompanied by phase transformation. This Minireview summarizes recent developments in growing research into photoresponsive molecular crystals. The basic mechanisms of different kinds of photomechanical materials are described in detail; recent advances in photomechanical crystals for promising applications as smart materials are also highlighted.

Accurate and precise control of the transition-metal ions in the docking sites of porous functional materials especially covalent-organic frameworks (COFs) is a challenging task in the synthesis of hybrid materials. In this work, we demonstrate the successful synthesis, characterization, and utilization of two stable vanadium docked COFs, namely VO-TAPT-2,3-DHTA and VO-PyTTA-2,3-DHTA as efficient heterogeneous catalysts for Mannich-type reactions. The obtained results revealed that the as-prepared vanadium-decorated COFs are robust and maintain framework crystallinity, reusability, and efficiency under the sway of electronic and steric effects. Significantly, this work opens up the opportunity for docking other metals and exploring practically and industrially important catalytic reactions.

Accumulation of high concentrations of Al(III) in body has a direct impact on health and therefore, the trace detection of Al(III) has been a matter for substantial concern. An anionic metal organic framework ({[Me2 NH2 ]0.5 [Co(DATRz)0.5 (NH2 BDC)] ⋅ xG}n ; 1; HDATRz=3,5-diamino-1,2,4-triazole, H2 NH2 -BDC=2-amino-1,4-benzenedicarboxylic acid, G=guest molecule) composed of two types of secondary building units (SBU) and channels of varying sizes was synthesized by employing a rational design mixed ligand synthesis approach. Free -NH2 groups on both the ligands are immobilized onto the pore surface of the MOF which acts as a superior luminescent sensor for turn-on Al(III) detection. Furthermore, the large channels could allow the counter-ions to pass through and get exchanged to selectively detect Al(III) in presence of other seventeen metal ions with magnificent luminescence enhancement. The observed limit of detection is as low as 17.5 ppb, which is the lowest among the MOF-based sensors achieved so far. To make this detection approach simple, portable and economic, we demonstrate MOF filter paper test for real time naked eye observation.

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.

Nature has long been a dominant source of inspiration in the area of chemistry, serving as prototypes for the design of materials with proficient performance. In this Feature article, we present our efforts to explore porous organic polymers (POPs) as a platform for the construction of biomimetic materials to enable new technologies to achieve efficient conversions and molecular recognition. For each aspect, we first present the chemical basis of nature, followed by depicting the principles and design strategies involved for functionalizing POPs along with a summary of critical requirements for materials, culminating in a demonstration of unique features of POPs. Our endeavours in using POPs to address the fundamental scientific problems related to biomimetic catalysis and adsorption are then illustrated to show their enormous potential and capabilities for applications ranging from concerted catalysis to radionuclide sequestration. To conclude, we present a personal perspective on the challenges and opportunities in this emerging field.

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.

Enzyme immobilization has been demonstrated to be a favorable protocol to promote industrialization of biomacromolecules. Despite tremendous efforts to develop new strategies and materials to realize this process, maintaining enzyme activity is still a formidable challenge. Herein we created a sacrificial templating method, using metal-organic frameworks (MOFs) as sacrificial templates to construct hollow covalent organic framework (COF) capsules for enzyme encapsulation. This strategy can provide a capacious microenvironment to unleash enzyme molecules. The improved conformational freedom of enzymes, enhanced mass transfer, and protective effect against the external environment ultimately boosted the enzymatic activities. We also found that this strategy possesses high versatility that is suitable for diverse biomacromolecules, MOF templates, and COF capsules. Moreover, the dimensions, pore sizes, and shell thickness of COF capsules can be conveniently tuned, allowing for customizing bioreactors for specific functions. For example, coencapsulation of different enzymes with synergistic functions were successfully demonstrated using this bioreactor platform. This study not only opens up a new avenue to overcome the present limitations of enzymatic immobilization in porous matrixes but also provides new opportunities for construction of biomicrodevices or artificial organelles based on crystalline porous materials.

peer-reviewed Fabrication of zeolite-like metal-organic frameworks (ZMOFs) for advanced applications such as enzyme immobilization is of great interest but represents a great synthetic challenge. Herein, we have developed a new strategy using proteins as structuredirected agents to direct the formation of new ZMOFs that can act as versatile platforms for in-situ encapsulation of proteins under ambient conditions. Notably, protein incorporation directs the formation of a ZMOF with a sodalite (sod) topology instead of a non-porous diamondoid (dia) topology under analogous synthetic conditions. An in-depth investigation into the mechanism of the encapsulation process revealed that histidine moieties in proteins played a crucial role in the observed templating effect. Modulating histidine content thereby influenced the resultant MOF product (from dia to dia + sod mixture and, ultimately, to sod MOF). Moreover, the resulting ZMOFs incorporated proteins and preserved their activity even after the stress of high temperatures and organic solvents. Specifically, biocatalysis and biopharmaceutical formulation applications are enabled. This study demonstrates the first example, to our knowledge, of proteins as structure-directed agents for new crystalline metal-organic materials and paves the way for in-situ incorporation of biomacromolecules into porous materials for multiple applications

The separation of racemic compounds is important in many fields, such as pharmacology and biology. Taking advantage of the intrinsically strong chiral environment and specific interactions featured by biomolecules, here we contribute a general strategy is developed to enrich chirality into covalent organic frameworks (COFs) by covalently immobilizing a series of biomolecules (amino acids, peptides, enzymes) into achiral COFs. Inheriting the strong chirality and specific interactions from the immobilized biomolecules, the afforded biomolecules⊂COFs serve as versatile and highly efficient chiral stationary phases towards various racemates in both normal and reverse phase of high-performance liquid chromatography (HPLC). The different interactions between enzyme secondary structure and racemates were revealed by surface-enhanced Raman scattering studies, accounting for the observed chiral separation capacity of enzymes⊂COFs.

Enzyme immobilization in metal-organic frameworks (MOFs) offers retained enzyme integrity and activity, enhanced stability, and reduced leaching. Trapping enzymes on MOF surfaces would allow for catalysis involving large substrates. In both cases, the catalytic efficiency and selectivity depend not only on enzyme integrity/concentration but also orientation. However, it has been a challenge to determine the orientation of enzymes that are supported on solid matrices, which is even more challenging for enzymes immobilized/trapped in MOFs due to the interferences of the MOF background signals. To address such challenge, we demonstrate in this work the utilization of site-directed spin labeling in combination with Electron Paramagnetic Resonance spectroscopy, which allows for the first time the characterization of the orientation of enzymes trapped on MOF surfaces. The obtained insights are fundamentally important for MOF-based enzyme immobilization design and understanding enzyme orientation once trapped in solid matrices or even cellular confinement conditions.

Summary Lewis pair (LP) chemistry has shown broad applications in the catalysis field. However, one significant challenge has been recognized as the instability for most homogeneous LP catalysts upon recycling, thus inevitably leading to dramatic loss in catalytic activity. Additionally, current heterogeneous LP catalysts suffer from low surface area, which largely limits their catalytic efficiency, thereby restricting their potential applications. In this work, we report the successful introduction of LPs, classical and frustrated, into a metal-organic framework (MOF) that features high surface and ordered pore structure via a stepwise anchoring strategy. Not only can the LP be stabilized by the strong coordination interaction between the LP and MOF, but the resultant MOF-LP also demonstrates excellent catalysis performance with interesting size and steric selectivity. Given the broad applicability of LPs, our work therefore paves a way for advancing MOF-LP as a new paradigm for catalysis.

Chemical transformations are highly sensitive toward changes in the solvation environment and solvents have long been used to control their outcome. Reactions display unique performance in solvents like ionic liquids or DMSO, however, isolating products from them is cumbersome and energy-consuming. Here, we develop promising alternatives by constructing solvent moieties into porous materials, which in turn serve as platforms for introducing catalytic species. Due to the high density of the solvent moieties, these porous solid solvents (PSSs) retain solvation ability, which greatly influences the performance of incorporated active sites via concerted non-covalent substrate–catalyst interactions. As a proof-of-concept, the -SO3H-incorporated PSSs exhibit high yields of fructose to 5-hydroxymethylfurfural in THF, which exceeds the best results reported using readily separable solvents and even rivals those in ionic liquids or DMSO. Given the wide application, our strategy provides a step forward towards sustainable synthesis by eliminating the concerns with separation unfriendly solvents., Solvents play important roles in chemical transformations, but isolating products from solvents is cumbersome and energy-consuming. Here, the authors develop promising alternatives by anchoring the solvent moieties onto porous materials for creating solvation environments in heterogeneous catalysts for efficient biomass conversion.