Synthesis of Bifunctional Porphyrin Polymers for Catalytic Conversion of Dilute CO 2 to Cyclic Carbonates

Development of efficient solid catalysts for catalytic conversion of dilute CO 2 is of extreme importance for carbon capture and utilization. We report the synthesis of bifunctional polymers co-incorporated with porphyrin-Zn as Lewis acid sites and Br – as nucleophiles for the cycloaddition of dilute CO 2 with epoxides in this work. It was found that the Br – /Zn ratio has a volcano relation with the activity of bifunctional polymers in a cycloaddition reaction, indicating the synergy effect between Lewis acid sites and nucleophiles. The turnover frequency (TOF) of the bifunctional polymer is more than four-fold that of the physical mixture of tetrabutylammonium bromide and porphyrin-Zn-incorporated polymer, implying the enhanced cooperation between Br – and porphyrin-Zn in the polymer network. The bifunctional polymer with optimized Br – /Zn afforded 99% conversion, 99% selectivity, and a TOF as high as 12,000 h –1 for the cycloaddition of CO 2 and propylene oxide, which is among the most active solid catalysts ever reported. Furthermore, the bifunctional polymer could efficiently catalyze the cycloaddition of epichlorohydrin with dilute CO 2 (7.5% CO 2 balanced by N 2 ) even under ambient conditions, demonstrating its potential application in industrial-scale production.