Triphenylimidazolium-incorporated, benzbisimidazole-linked porous organic polymers as efficient catalyst for CO2 conversion

The cycloaddition of CO2 to epoxides is now becoming one of the most important CO2-fixation reactions due to the 100% atom efficiency together with the wide application of cyclic carbonates. However, such a cycloaddition reaction often requires efficient catalysts owing to the intrinsically inert nature of CO2. Herein, we report the synthesis of triphenylimidazolium-incorporated, benzbisimidazole-linked porous organic polymer (namely PBPI-IL) by polycondensation of 1,2,4,5-benzenetetramine with triphenylimidazole-containing tetraaldehyde followed by post-treatment with iodomethane. The as-synthesized PBPI-IL2 network with intact benzbisimidazole ring possesses an ionization degree of 31.94 mol% and a specific surface area of 350 m(2) g(-1), which is capable of efficiently catalyzing the cycloaddition of CO2 to epoxides, i.e., 99% conversion and 99% selectivity in the transformation of epichlorohydrin at 60 degrees C under atmospheric CO2 pressure. Moreover, the PBPI-IL2 network can be readily recycled and reused for at least 6 times. The highly catalytic activity of PBPI-IL2 network can be ascribed to the H-bonding interaction between benzbisimidazole ring and epoxides, the Lewis base-Lewis acid and pi-pi bonding interactions between benzbisimidazole ring and CO2 molecule, as well as the high nucleophilicity of I- anion.

Automated summary

The cycloaddition of CO2 to epoxides is an important CO2-fixation reaction, and this study introduces a new porous organic polymer, PBPI-IL2, which exhibits high catalytic activity for this reaction. PBPI-IL2 shows high conversion and selectivity in the cycloaddition of CO2 to epoxides, and it can be recycled and reused.