Synergistic catalysis of hypercrosslinked ionic polymers with multi-ionic sites for conversion of CO2 to cyclic carbonates

Abstract

High catalytic activity for the conversion of CO2 into cyclic carbonates requires the preparation of porous ionic catalysts with multi-active sites and high ionic density. Herein, a series of hypercrosslinked ionic polymers (HIPs) with multi-ionic sites, high ionic density and hydrogen bond donors (imino group) were synthesized through the one-pot Friedel–Crafts alkylation and post-synthetic strategies. Adsorption measurements showed that HIPs exhibited outstanding CO2 uptakes (1.80−2.97 mmol g − 1, 273 K and 1 bar). Importantly, under the synergistic effects of multi-ionic sites, high ionic density and hydrogen bond donors, the metal-free catalyst HBIM(0.5)@QA-Br showed excellent catalytic yield (99%) and selectivity (99%) for cycloaddition of CO2 with epichlorohydrin at 140 °C, 0.1 MPa CO2 in 2 h. By extending the time appropriately, high catalytic yields (styrene oxide, 140 °C, 4 h, 99% yield; 120 °C, 6.5 h, 93% yield; 100 °C, 16 h, 94% yield) were achieved at low temperature. In addition, the catalyst can be easily reused with stable recyclability. This work not only provides a new strategy to prepare metal-free porous ionic catalysts with multi-ionic sites and hydrogen bond donors but also demonstrated that the synergistic catalysis of multi-ionic sites is helpful to promote CO2 conversion.