Porous Supramolecular Crystalline Materials for Photocatalysis.

Porous supramolecular crystalline materials (PSCMs), such as hydrogen-bonded organic frameworks (HOFs), π frameworks, can be defined as a type of porous supramolecular assemblies stabilized by hydrogen-bonding, π-π stacking and other non-covalent interactions. Benefiting from the unique features of mild synthesis conditions, well-defined and synthetically tailorable structures, easy healing and regeneration, PSCMs have garnered widespread interest in research fields including molecular recognition, sensor, gas storage and separation. Moreover, they have emerged as promising photocatalysts because these PSCMs could be readily endowed with optical function, and the hydrogen-bonding and π-π stacking can offer channels for electron transfer to boost the photocatalytic activity.

A Supramolecular-Nanocage-Based Framework Stabilized by π-π Stacking Interactions with Enhanced Photocatalysis.

π frameworks, defined as a type of porous supramolecular materials weaved from conjugated molecular units by π-π stacking interactions, provide a new direction in photocatalysis. However, such examples are rarely reported. Herein, we report a supramolecular-nanocage-based π framework constructed from a photoactive Cu(I) complex unit.

Modulating the Microenvironments of Robust Metal Hydrogen-Bonded Organic Frameworks for Boosting Photocatalytic Hydrogen Evolution.

Hydrogen-bonded organic frameworks (HOFs) are outstanding candidates for photocatalytic hydrogen evolution. However, most of reported HOFs suffer from poor stability and photocatalytic activity in the absence of Pt cocatalyst. Herein, a series of metal HOFs (Co-HOF-X, X=COOMe, Br, tBu and OMe) have been rationally constructed based on dinuclear cobalt complexes, which exhibit exceptional stability in the presence of strong acid (12 M HCl) and strong base (5 M NaOH) for at least 10 days.

Covalent Bonding of Salen Metal Complexes with Pyrene Chromophores to Porous Polymers for Photocatalytic Hydrogen Evolution.

The development of low-cost and efficient photocatalysts to achieve water splitting to hydrogen (H) is highly desirable but remains challenging. Herein, we design and synthesize two porous polymers (Co-Salen-P and Fe-Salen-P) by covalent bonding of salen metal complexes and pyrene chromophores for photocatalytic H evolution. The catalytic results demonstrate that the two polymers exhibit excellent catalytic performance for H generation in the absence of additional noble-metal photosensitizers and cocatalysts.

Boosting CO Photoreduction to Formate or CO with High Selectivity over a Covalent Organic Framework Covalently Anchored on Graphene Oxide.

Covalent organic frameworks (COFs) have been widely studied in photocatalytic CO reduction reaction (CO RR). However, pristine COFs usually exhibit low catalytic efficiency owing to the fast recombination of photogenerated electrons and holes. In this study, we fabricated a stable COF-based composite (GO-COF-366-Co) by covalently anchoring COF-366-Co on the surface of graphene oxide (GO) for the photocatalytic CO reduction.

Water-Etched Approach to Hierarchically Porous Metal-Organic Frameworks with High Stability.

The development of hierarchically porous metal-organic frameworks (MOFs) with high stability is desirable to expand their applications but remains challenging. Herein, an anionic sodalite-type microporous MOF (; TTCA = triphenylene-2,6,10-tricarboxylate) was synthesized, which shows outstanding catalytic activities for the cycloaddition of CO into cyclic carbonates. Moreover, the microporous can be transformed into a hierarchical micro- and mesoporous by water treatment with the mesopore sizes of 2 to 12 nm.

Dinuclear metal synergistic catalysis for energy conversion.

Catalysts featuring dinuclear metal sites are regarded as superior systems compared with their counterparts with mononuclear metal sites. The dinuclear metal sites in catalysts with appropriate spatial separations and geometric configurations can confer the dinuclear metal synergistic catalysis (DMSC) effect, and thus boost the catalytic performance, in particular for reactions involving multiple reactants, intermediates and products. In this review, we summarize the related reports on the design and synthesis of both homogeneous and heterogeneous dinuclear metal catalysts, and their applications in energy conversion reactions, including photo-/electro-catalytic hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), CO reduction reaction (CORR), and N reduction reaction (NRR).

Modulating the Electronic Structures of Dual-Atom Catalysts via Coordination Environment Engineering for Boosting CO Electroreduction.

Dual-atom catalysts (DACs) have emerged as efficient electrocatalysts for CO reduction owing to the synergistic effect between the binary metal sites. However, rationally modulating the electronic structure of DACs to optimize the catalytic performance remains a great challenge. Herein, we report the electronic structure modulation of three Ni DACs (namely, Ni -N , Ni -N C and Ni -N C ) by the regulation of the coordination environments around the dual-atom Ni centres.

Ordered heterogeneity of molecular photosensitizer toward enhanced photocatalysis.

SignificanceThe photosensitizer is one of the important components in the photocatalytic system. Molecular photosensitizers have well-defined structures, which is beneficial in revealing the catalysis mechanism and helpful for further structural design and performance optimization. However, separation and recycling of the molecular photosensitizers is a great problem.

Incorporation of Chromophores into Metal-Organic Frameworks for Boosting CO Conversion.

The exploitation of highly stable and active catalysts for the conversion of CO into valuable fuels is desirable but is a great challenge. Herein, we report that the incorporation of chromophores into metal-organic frameworks (MOFs) could afford robust catalysts for efficient CO conversion. Specifically, a porous Nd(III) MOF (; TTCA = triphenylene-2,6,10-tricarboxylate) was constructed by incorporating one-dimensional Nd(CO) chains and TTCA ligands, which exhibits a very high stability, retaining its framework not only in the air at 300 °C for 2 h but also in boiling aqueous solutions at pH 1-12 for 7 days.

Regulating Photocatalysis by Spin-State Manipulation of Cobalt in Covalent Organic Frameworks.

While catalysis is highly dependent on the electronic structure of the catalyst, the understanding of catalytic performance affected by electron spin regulation remains challenging and rare. Herein, we have developed a facile strategy to the manipulation of the cobalt spin state over covalent organic frameworks (COFs), COF-367-Co, by simply changing the oxidation state of Co centered in the porphyrin. Density functional theory (DFT) calculations together with experimental results confirm that Co and Co are embedded in COF-367 with = 1/2 and 0 spin ground states, respectively.

A Way for Derived Carbon Materials by Thermal Etching Hybrid Borate for Electrochemical CO Reduction.

Two hybridized skeleton borates [Zn(en)][BO(OH)] (; en = ethylenediamine) and [Cd(1,3-dap)][BO(OH)]HO (; 1,3-dap = 1,3-diaminopropane) were solvothermally synthesized. The boron oxide clusters formed 2D planes, and these planes formed a 3D structure through co-oxygen links of metal complexes. Herein, a novel strategy has been developed, i.

π-π stacking interactions: Non-negligible forces for stabilizing porous supramolecular frameworks.

Revealing the contribution of π-π stacking interactions in supramolecular assembly is important for understanding the intrinsic nature of molecular assembly fundamentally. However, because they are much weaker than covalent bonds, π-π stacking interactions are usually ignored in the construction of porous materials. Obtaining stable porous materials that are only dependent on π-π stacking interactions, despite being very challenging, could address this concern.

Regulating the Coordination Environment of MOF-Templated Single-Atom Nickel Electrocatalysts for Boosting CO Reduction.

The general synthesis and control of the coordination environment of single-atom catalysts (SACs) remains a great challenge. Herein, a general host-guest cooperative protection strategy has been developed to construct SACs by introducing polypyrrole (PPy) into a bimetallic metal-organic framework. As an example, the introduction of Mg in MgNi-MOF-74 extends the distance between adjacent Ni atoms; the PPy guests serve as N source to stabilize the isolated Ni atoms during pyrolysis.

Facile Exfoliation of 3D Pillared Metal-Organic Frameworks (MOFs) to Produce MOF Nanosheets with Functionalized Surfaces.

The production of two-dimensional (2D) ultrathin metal-organic framework (MOF) nanosheets with functionalized surfaces is significant for extending their applications. To date, no protocol has been developed yet to solve this problem. Herein, we report a facile, mild, and efficient method to produce 2D monolayer MOF nanosheets with hydrophobic surfaces from layer-pillared 3D MOFs.

A Lanthanum Carboxylate Framework with Exceptional Stability and Highly Selective Adsorption of Gas and Liquid.

The development of porous metal-organic frameworks that can retain structural integrity under harsh physical and chemical conditions is essential from the perspective of their use in adsorption, catalysis, and sensors. Herein, a lanthanum carboxylate framework was found to exhibit exceptional stability, not only robust in boiling aqueous solutions at pH 2-12 and in boiling common organic solvents over 24 h but also stable upon ball milling for 1 h. Furthermore, this framework displayed highly selective separation for CO over N ( S = 940), as well as size-dependent selective adsorption behavior of water and alcohols.

Photochromism, photoluminescence modulation and selective recognition of small molecules of two highly stable dynamic metal-organic frameworks.

Two highly stable dynamic metal-organic frameworks exhibit photochromism, tunable photoluminescence, and selective detection of oxygen, which can be recognised by the naked eye through color changes. Furthermore, they also display selective recognition of benzyl alcohol and halogenated solvents, respectively.

Two bilayer metal-organic frameworks with rare trinuclear heterometal clusters and tunable photoluminescence.

Two bilayer metal-organic frameworks (MOFs) respectively containing trinuclear Pb/K and Cd/Na clusters have been solvothermally synthesized. Photoluminescence studies showed that they exhibit tunable purple-to-red-to-green and purple-to-green luminescence behaviours by variation of excitation light, respectively.

Two Li-Zn Cluster-Based Metal-Organic Frameworks: Strong H/CO Binding and High Selectivity to CO.

Two metal-organic frameworks (MOFs) {(MeNH)[ZnLi(PTCA)(HO)]}·n{3DMF·CHO·4HO} (1) and {(MeNH)[ZnLi(PTCA)]}·n{3DMF·5HO} (2) have been constructed from Li-Zn clusters and pyrene-1,3,6,8-tetracarboxylic acid (HPTCA) under solvothermal conditions. Gas sorption measurements have revealed that the pore of desolvated 2 (2d) can strongly interact with H and CO, with high H and CO adsorption heats of 15.3 and 51.

Photoinduced water oxidation by an organic ligand incorporated into the framework of a stable metal-organic framework.

A major challenge for the development of organic water oxidation catalysts is their low chemical stability and low catalytic efficiency. Herein, we first demonstrate that both the chemical stability and catalytic efficiency of an organic ligand for water oxidation can be improved by incorporating it into the framework of a stable MOF. This opens up a promising avenue for the development of stable and efficient organic water oxidation catalysts.

Uncovering the Role of Metal Catalysis in Tetrazole Formation by an In Situ Cycloaddition Reaction: An Experimental Approach.

Using an experimental approach, the role of metal catalysis has been investigated in the in situ cycloaddition reaction of nitrile with azide to form tetrazoles. It has been shown that metal catalysis serves to activate the cyano group in the nitrile reagent by a coordinative interaction.

A luminescent microporous metal-organic framework with highly selective CO₂ adsorption and sensing of nitro explosives.

A luminescent microporous metal-organic framework based on a π-electron-rich tricarboxylate ligand and an In(3+) ion has been solvothermally obtained and characterized and exhibits highly selective CO2 adsorption over CH4 and N2 gases and selective sensing of the nitro explosive 2,4,6-trinitrophenol.

Temperature-induced transitions of self-assembled phthalocyanine molecular nanoarrays at the solid-liquid interface: from randomness to order.

A promising approach to create functional nanoarrays is supramolecular self-assembly at liquid-solid interfaces. In the present investigation, we report on the self-assembly of phthalocyanine arrays using triphenylene-2,6,10-tricarboxylic acid (H₃TTCA) as a molecular nanotemplate. Five different metastable arrays are achieved in the study, including a thermodynamically stable configuration.

A highly stable dynamic fluorescent metal-organic framework for selective sensing of nitroaromatic explosives.

A dynamic fluorescent metal-organic framework has been constructed using triphenylene-2,6,10-tricarboxylate and Tb(3+) as building blocks, which exhibits guest-responsive structural dynamism and selective sensing of nitroaromatic explosives.