Metalloporphyrin- and Phosphonium-Bifunctionalized Porous Organic Polymers for Efficient Synergistic Catalysis of CO2 Conversion under Mild Conditions

Functional porous organic polymers (POPs) have been widely developed as heterogeneous catalysts for carbon dioxide (CO2) conversion. However, the integration of multifunctional active sites into POPs remains a major challenge. Herein, a facile postsynthesis modification strategy was explored to fabricate metalloporphyrin- and phosphonium-bifunctionalized POPs (TAPPM-PTBAR) as the heterogeneous catalysts for CO2 conversion. The as-developed catalysts were characterized in detail using various techniques. The results illustrated that the novel POP catalysts featured abundant Lewis acid metal centers, nucleophilic active sites, and phosphonium cation. These features enabled the catalyst to immobilize CO2 under mild and solvent-free conditions. The synergistic effect of cobalt as a Lewis acid site and halide anion as a bifunctional nucleophile site enhances the catalysis performance of TAPPM-PTBAR. Combining the experimental results and density functional theory calculation, a plausible reaction mechanism involving hydrogen bonding and Co3+ center for epoxides was proposed. Considering its good reusability and substrate expansibility, the developed TAPPCo(3+)-PTBANH(2) demonstrated great potential as a robust heterogeneous catalyst for the efficient utilization of C1 resources.