Facile fabrication of a heterogeneous Co-modified pyridinecarboxaldehyde-polyethylenimine catalyst for efficient CO2 conversion under mild conditions†
A heterogeneous Co-modified pyridinecarboxaldehyde-polyethylenimine catalyst (Co-Py-PEI) with highly active metal sites and amine groups was facilely prepared and thoroughly characterized. The novel Co-Py-PEI catalyst together with Bu4NBr exhibited efficient catalytic properties for the conversion of CO2 into cyclic carbonates under the mild conditions of 80 °C, 1.0 MPa and 5 h, and 99% yield of propylene carbonate was obtained even in combination with 7.2 mol% Bu4NBr loading under the conditions of room temperature, 1.0 MPa and 24 h. The high activity for CO2 cycloaddition reaction to generate cyclic carbonate was ascribed to the synergistic catalysis of Lewis acid–base sites and bromide ions in the Co-Py-PEI/Bu4NBr catalyst system. Moreover, the Co-Py-PEI catalyst exhibited outstanding thermal and structural stability, besides its simple recovery by centrifugation and its excellent recyclability of up to seven runs. Thus, the Co-Py-PEI catalyst is considered to be a satisfactory candidate for the coupling reaction of CO2 and epoxides.