Dihydroxy functionalized binuclear carbonate based poly(ionic liquid)s for highly efficient conversion of low-concentration CO₂ into cyclic carbonate

The elimination of carbon dioxide (CO₂) from the industrial post-combustion dilute CO₂ has been a hot issue and the selective conversion of CO₂ from the exhaust gas stream still remains a challenge. Herein, dihydroxy functionalized binuclear carbonate based poly(ionic liquid)s (HB-PILs) were prepared for conversion of low-concentration CO₂ from the dilute CO₂ (15 vol% CO₂ + 85 vol% N₂) into cyclic carbonate. Using epichlorohydrin as a probe substrate, the obtained HB-PILs exhibited excellent catalytic performance for the CO₂ cycloaddition reaction. Under optimized process parameters (100 ℃, 2 MPa and 4 h), the highest yield (95 %) of chloropropene carbonate (CPC) was obtained, which was comparable to the previous reported results. Moreover, the synergetic effect between the activation of epoxides by dihydroxyl groups and the adsorption of CO₂ by basic CO₃^2- ions was studied through the theoretical calculations. DFT results indicated that CO₃^2- served as the nucleophilic site, working synergistically with hydrogen bond donors to facilitate the ring-opening of epichlorohydrin (ECH). Additionally, CO₃^2- functioned as the basic site to activate CO₂. This study will provide a promising solution for mitigating global climate change and advancing the green chemistry of CO₂ utilization from dilute CO₂.