Bottom-Up Assembly of a Highly Efficient Metal-Organic Framework for Cooperative Catalysis

In this study, we demonstrate a bottom-up assembly of a monomeric copper complex and a two-dimensional (2-D) heterometallic metal-organic framework (MOF) from a carboxylate-functionalized tridentate Schiff base ligand and metal ions. The obtained 2-D MOF features a unique bimetallic copper center which is different from its monometallic precursor and acts as an efficient heterogeneous catalyst for the Friedel-Crafts reaction and Henry reaction. The MOF catalyst shows a remarkably superior activity compared to its homogeneous counterparts in a wide range of substrates. It is presumably ascribed to the dual activation of the substrates by the active bimetallic copper center confined in the MOF network, which is supported by the significant changes in catalytic activity at low catalyst/substrates ratios when using the 2-D MOF and its precursor as catalysts, respectively. Moreover, the MOF catalyst also shows an excellent stability and recyclability. Our work, therefore, provides a stepwise strategy to design a heterogeneous cooperative catalyst, by taking advantage of the modulated structure of MOF and tunable functionality of the tridentate Schiff base, with high performance in a variety of organic synthesis.