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

Abstract

A novel polyoxovanadate-based copper(I)–organic framework, [Cu^I(bib)]₄{V^V₄O₁₂} (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 α-alkylidene cyclic carbonates at room temperature, and the conversion and selectivity are almost 100%. More importantly, no obvious decrease in the yield of the α-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 CC 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 α-alkylidene cyclic carbonates at room temperature.