High‐Nuclearity Polyoxometalate‐Based Metal‐Organic Frameworks for Photocatalytic Oxidative Cleavage of C‐C Bond

Abstract

High‐nuclearity polyoxometalate (POM) clusters are attractive building blocks (BBs) for the synthesis of metal‐organic frameworks (MOFs) due to their high connectivity and inherently multiple metal centers as functional sites. This work demonstrates a strategy of step‐wise growth on ring‐shaped [P8W48O184]40‐ precursor, which produced two new high‐nuclearity polyoxotungstates, a half‐closed [H16P8W58O218]32‐ {W58} and a fully‐closed [H16P8W64O236]32‐ {W64}. By in‐situ synthesis, unique MOFs of copper triazole‐benzoic acid (HL) complexes incorporating the negatively‐charged {W58} and {W64} as nodes, {Cu11(HL)8LW58} HNPOMOF‐1 and {Cu9(HL)9W64} HNPOMOF‐2, were constructed by delicately tuning the reaction conditions, mainly solution pH, which controls the formation of {W58} and {W64}, and at the same time the protonation of triazole‐benzoic acid ligand thus its coordination mode to copper ion that creates the highest nuclearity POM‐derived MOFs reported to date. HNPOMOF‐1 features 3D framework possessing cage‐like cavities filled with exposed carboxyl groups, while the inherent 2D layer‐like HNPOMOF‐2 allows for facile exfoliation into ultrathin nanosheets, and the resulted HNPOMOF‐2NS exhibits superior activity towards photocatalytic oxidative cleavage of C‐C bond for a series of lignin models. This work not only provides a strategy to build high‐nuclearity POM cluster‐based frameworks, but also demonstrates their great potential as functional materials for green catalysis.