Preparation of several novel Salen-Co(III) visible photocatalysts and their application in the copolymerization of carbon dioxide with propylene oxide

Carbon dioxide (CO2) is a renewable carbon source, which can be copolymerized with epoxide to prepare aliphatic polycarbonate and cyclic carbonate. In this paper, a series of novel SalenCo(III) photocatalysts were synthesized for the first time, and the copolymerization of CO2 and propylene oxide (PO) was studied. The effects of reaction conditions on catalytic activity and selectivity were investigated. The results show that the catalyst 3 with strong polarity Schiff base and planar conjugated dye has the highest activity and selectivity for CO2 and PO photocopolymerization among the four SalenCo(III) photocatalysts. Due to the synergistic action of the catalyst and Mn4Ca nanocluster, the ring-opening of PO is promoted and the photocatalytic efficiency is greatly improved. The introduction of visible light improves the catalytic efficiency, and increasing light intensity can better improve the catalytic efficiency. The optimal copolymerization condition was 60 °C, 6 h, 200 W, 2 MPa of CO2 with Mn4Ca nanocluster/catalyst 3.