Efficient CO₂ enrichment and fixation by engineering micropores of multifunctional hypercrosslinked ionic polymers

Efficient chemical fixation of carbon dioxide (CO₂) into valuable fine chemicals requires porous materials with highly active catalytic centers. Herein, multifunctional imidazolium based hypercrosslinked ionic polymers with versatile functional groups (sulfonic, hydroxyl, amino, carboxyl, and alkyl group), abundant microporosity and high ionic site density were constructed in a two-step solvothermal route including free-radical copolymerization of divinylbenzene (DVB), 4-vinylbenzyl chloride (VBC) and imidazolium bromide ionic liquids (ILs) and successive Friedel-Crafts alkylation based hypercrosslinkage. The resultant hydroxyl-functional ionic polymer demonstrated promising performances in selective adsorption and conversion of CO₂ via cycloaddition with epoxide. High yield associating with large turnover number (TON) and turnover frequency (TOF), stable reusability and well substrate compatibility were achieved, affording an efficient metal-free heterogeneous catalyst for CO₂ fixation. The full microporous structure resulted in CO₂ enrichment around the robust hydroxyl-functional ionic sites, showing a synergistic effect to promote CO₂ transformation.