Highly efficient conversion of CO₂ at atmospheric pressure to cyclic carbonates with in situ-generated homogeneous catalysts from a copper-containing coordination polymer

A copper-containing coordination polymer ((CuL)_n, L = (Z)-2-(5-chlorin-2-hydroxy benzylideneamino) acetic acid, namely BIT-C), was facilely synthesized and structurally analyzed by single-crystal X-ray diffraction. BIT-C has an outstanding catalytic activity for the conversion of atmospheric pressure CO₂ and various epoxides to cyclic carbonates. Several quaternary ammonium halides, ionic liquids, and organic bases were illustrated to be effective co-catalysts. Using BIT-C, Bu₄NBr, and phenyl glycidyl ether, direct capture and conversion of CO₂ from the air was shown to be feasible at the room temperature, with 19% yield of phenoxy propylene carbonate. During reaction, multistage dissociation of BIT-C was detected. The binuclear Cu fragment ((CuL)₂) was demonstrated to be essential active species in catalysis and unable to be generated from the raw materials of BIT-C but currently only from the multistage dissociation of BIT-C. Kinetic analysis and DFT calculations suggest a reaction mechanism where a copper center activates epoxides and CO₂ successively.