A highly stable polyoxovanadate-based Cu(i)-MOF for the carboxylative cyclization of CO2 with propargylic alcohols at room temperature

A novel polyoxovanadate-based copper(i)-organic framework, [Cu-I(bib)](4){(V4O12)-O-V} (V-Cu-MOF, bib = 1,4-bis(1H-imidazoly-1-yl)benzene), is facilely synthesized under mild hydrothermal conditions. The structure of the V-Cu-MOF is constructed from a cyclic {V4O12}(4-) polyanion cluster and a 1D chain Cu(i)-MOF ([Cu-I(bib)](+)). The presence of the {V4O12}(4-) cluster stabilizes the Cu(i)-MOF with Cu(i) as the center, thereby improving the stability of the V-Cu-MOF and enabling it to stably exist in various solvents and pH = 2-12 solutions. Additionally, the V-Cu-MOF as a heterogeneous catalyst can catalyze the carboxylative cyclization of CO2 and propargylic alcohols to high value-added alpha-alkylidene cyclic carbonates at room temperature, and the conversion and selectivity are almost 100%. More importantly, no obvious decrease in the yield of the alpha-alkylidene cyclic carbonate is observed after ten cycles. These results indicate the excellent catalytic activity and sustainability of the V-Cu-MOF. Research on the mechanism of the catalytic reaction suggests that the high-density Cu(i) sites in the V-Cu-MOF are the catalytically active centers for activating the Cxe002;C bonds of propargylic alcohols. To the best of our knowledge, this is the first example of polyoxometalate-based metal-organic framework catalyst for catalyzing the conversion of CO2 to value-added alpha-alkylidene cyclic carbonates at room temperature.