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

Abstract

The cycloaddition of CO 2 to epoxides is now becoming one of the most important CO 2 -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 CO 2 . 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 CO 2 to epoxides, i.e., 99% conversion and 99% selectivity in the transformation of epichlorohydrin at 60 °C under atmospheric CO 2 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 π-π bonding interactions between benzbisimidazole ring and CO 2 molecule, as well as the high nucleophilicity of I − anion. • PBPI is prepared by polycondensation of BPI with BTAT. • PBPI-IL is obtained through the post-treatment with CH 3 I. • PBPI-IL can catalyze the cycloaddition of CO 2 to epoxides under mild conditions. • The conversion of epichlorohydrin and selectivity can reach up to 99% and 99%. • The PBPI-IL2 catalyst can be readily recycled and reused for at least 6 times.