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 CO 2 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 CO 2 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 activity for cycloaddition of CO 2 with various epoxides, and the 99% yield and 99% selectivity of chloropropylene carbonate were obtained at 140 ℃, 0.1 MPa CO 2 in 2 h. By extending the time appropriately, high catalytic yields (styrene oxide, 140 ℃, 4 h, 99% yield; 120 ℃, 6.5 h, 93% yield; 100 ℃, 16 h, 94% yield) can still be obtained 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 HIPs catalysts with multi-ionic sites and hydrogen bond donors by utilizing and activating most of the reaction sites on imidazoline but also demonstrated that the synergistic catalysis of multi-ionic sites is contributed to improving the catalytic performance of HIPs for CO 2 cycloaddition reaction.

Keywords: CO2 cycloaddition, Hypercrosslinked ionic polymers, multi-ionic sites, synergistic catalysis.