Benzimidazolium-Decorated Metalloporphyrin Molecule and Polymer: a Reliable Preparation Method and Application in Catalyzing the Cycloaddition Reaction of CO2 and Epoxides

Graphical Metalloporphyrin molecule and polymer containing benzimidazolium units were synthesized via a novel method as bifunctional catalysts for the cycloaddition of CO 2 and epoxides. Due to the synergistic effect of central metal and halide anion, cationic metalloporphyrins and derivatives exhibit outstanding catalytic activities for the cycloaddition reaction of epoxides and carbon dioxide. Herein, a generic strategy was developed to synthesize the benzimidazolium-containing metalloporphyrin molecule and polymer. To demonstrate the method feasibility, we firstly synthesized the molecule 1 H , in which the benzimidazole groups were in-site constructed by the cyclization of 5,10,15,20-(4-carboxyphenyl)-porphyrin ( H 2 TCPP ) with o -diaminobenzene ( PEA ). After post-synthetic ionization and metallization, I − and Zn 2+ were introduced as the nucleophile and Lewis acid, respectively. The structure of 1 ZnIL was confirmed by single crystal X-ray diffraction analysis. By using the similar conditions of model reaction, H 2 TCPP was copolymerized with 1,2,4,5-tetraaminobenzene ( BTA ) to prepare the polymer P-1 ZnIL . The prepared cationic molecule 1 ZnIL and polymer P-1 ZnIL showed comparable activities in catalyzing the cycloaddition of carbon dioxide with epoxides to cyclic carbonates compared to the reported bifunctional catalysts based on metalloporphyrins.