Tailoring Crystal Facets of Metal–Organic Layers to Enhance Photocatalytic Activity for CO 2 Reduction

Linker Scissoring Strategy Enables Precise Shaping of Metal-Organic Frameworks for Chromatographic Separation

Precise shaping of metal-organic frameworks (MOFs) is significant in both fundamental coordination chemistry and practical applications, such as catalysis, separation, and biomedicine. Herein, we demonstrated a linker scissoring strategy for precisely shaping MOFs through surface conformational pairing. In this strategy, the bidentate linkers which were designed according to the original tetratopic ligands and the coordination environment of MOF surfaces, were utilized as the covering agents. The shape of these covering agents and the surface conformation of metals onto MOFs restricted them to coordinate on specific MOF facets thus precisely controlling the shape of the MOFs. Different shapes of PCN-608 from nanoplate (PCN-NP) to nanorod (PCN-NR) have been targeted by adding different bidentate linkers. The universality of this strategy was demonstrated by controlling the shapes of the NU-MOFs from nanoplate to nanorod. This strategy provides a new guiding principle to synthesize MOF nanocrystals with controlled shapes.

Cu3(BTC)2 nanoflakes synthesized in an ionic liquid/water binary solvent and their catalytic properties

Low-dimensional metal-organic frameworks (MOFs) exhibit enhanced properties compared with three-dimensional (3D) geometry MOFs in many fields. In this work, we demonstrate the synthesis of Cu₃(BTC)₂ (BTC = benzene-1,3,5-tricarboxylate) nanoflakes in a binary solvent of ionic liquid (IL) and water. Such a MOF architecture has a high surface area and abundant unsaturated coordination metal sites, making them attractive for adsorption and catalysis. For example, in catalyzing the oxidation reactions of a series of alcohols, the Cu₃(BTC)₂ nanoflakes exhibit a high performance that is superior to Cu₃(BTC)₂ microparticles synthesized in a conventional solvent. Experimental and theoretical studies reveal that the IL accelerates the crystallization of Cu₃(BTC)₂, while water plays a role in stripping the Cu₃(BTC)₂ blocks that are formed at an early stage through its attack on the crystal plane of Cu₃(BTC)₂. Such an in situ crystallization-exfoliation process that uses an IL/water solvent opens a new route for producing low-dimensional MOFs.

Building 2D/2D CdS/MOLs Heterojunctions for Efficient Photocatalytic Hydrogen Evolution

2D lamellar materials can offer high surface area and abundant reactive sites, thus showing an appealing prospect in photocatalytic hydrogen evolution. However, it is still difficult to build cost-efficient photocatalytic hydrogen evolution systems based on 2D materials. Herein, an in situ growth method is employed to build 2D/2D heterojunctions, with which 2D Ni-based metal-organic layers (Ni-MOLs) are closely grown on 2D porous CdS (P-CdS) nanosheets, affording traditional P-CdS/Ni-MOL heterojunction materials. Impressively, the optimized P-CdS/Ni-MOL catalyst exhibits superior photocatalytic hydrogen evolution performance, with an H₂ yield of 29.81 mmol g^-1 h^-1 . This value is 7 and 2981 times higher than that of P-CdS and Ni-MOLs, respectively, and comparable to those of reported state of the art catalysts. Photocatalytic mechanism studies reveal that the enhanced photocatalytic performance can be attributed to the 2D/2D intimate interface between P-CdS and Ni-MOLs, which facilitates the fast charge carriers' separation and transfer. This work provides a strategy to develop 2D MOL-based photocatalysts for sustainable energy conversion.

Computational Study of Double Transition Metal Atom Anchored on Graphdiyne Monolayer for Nitrogen Electroreduction

Converting N₂ to NH₃ is an essential reaction but remains a great challenge for industries. Developing more efficient catalysts for N₂ reduction under mild conditions is of vital importance. In this work, double transition metal atoms (TM=Mo, W, Nb and Ru) anchored on graphdiyne monolayer (TM₂ @GDY) as electrocatalysts are designed, and the corresponding reaction mechanisms of N₂ electroreduction are systematically investigated by means of first-principles calculations. The results show that the double TM atoms can be strongly anchored on the acetylenic ring of GDY and Ru₂ @GDY exhibits the highest catalytic activity for NRR with a maximum free energy change of 0.55 eV through the enzymatic pathway. The significant charge transfer between the substrate and the adsorbed N₂ molecule is responsible for the superior catalytic activity. This work could provide a new approach for the rational design of double-atom catalysts for NRR and other related reduction reactions.