An efficient mixed-valence copper pyrazolate catalyst for the conversion of carbon dioxide and epoxides into cyclic carbonates

Abstract

In this paper, a cyclic (Cu^Ipz)₃·CH₃CN (1) precursor and a mixed-valence pentanuclear complex Cu^I₃Cu^II₂(OH)pz₆·CH₃CN (2) have been synthesized and structurally characterized by single-crystal X-ray diffraction, where pzH = 4-chloro-3,5-diphenylpyrazole. The excellent catalytic activity of 2 has been demonstrated in the chemical fixation of CO₂ into value-added cyclic carbonates, which can be carried out at ambient pressure and room temperature along with ultra-high yield and perfect steric hindrance tolerance. Based on density functional theory (DFT) calculations and comparison with the catalytic performance of 1, it is proposed that the coordinatively unsaturated Cu^II atoms of 2 are probably the active sites for this catalytic reaction.