Microwave‐assisted fabrication of a mixed‐ligand [Cu 4 (μ 3 ‐OH) 2 ]‐cluster‐based metal–organic framework with coordinatively unsaturated metal sites for carboxylation of terminal alkynes with carbon dioxide

The development of efficient and stable metal–organic framework (MOF) catalysts with coordinatively unsaturated metal sites for modern organic synthesis is greatly important. Herein, a robust [Cu 4 (μ 3 ‐OH) 2 ]‐cluster‐based MOF (Cu‐MOF) with a mixed‐ligand system was successfully fabricated by a microwave‐assisted method under mild conditions. The as‐prepared Cu‐MOF catalyst possessing unsaturated Cu (II) sites exhibited excellent catalytic activity toward the direct carboxylation of 1‐ethynylbenzene with CO 2 , and various propiolic acid derivatives were synthesized in moderate to good yields under optimized reaction conditions. Furthermore, the catalyst remained stable and could be easily recycled for five sequential runs without incredible decrease in catalytic efficiency.