Guanidine-functionalized basic binuclear poly(ionic liquid)s for low partial pressure CO₂ fixation into cyclic carbonate

The direct conversion of low partial pressure (10–15 %) from industrial waste gas into high value-added chemicals provides a favorable solution to global climate change. However, developing high-efficient catalysts for the conversion of low partial pressure CO₂ under mild conditions is still a major challenge. Here, guanidine-functionalized basic binuclear poly(ionic liquid)s (P-DBTMGH) were prepared by free radical copolymerization. With the introduction of guanidine ionic liquids into the framework of GB-PILs, the alkalinity in the structure was improved, and thus enhancing CO₂ surface adsorption and activation ability. Meanwhile, bromide containing binuclear sites help to increase the ion density of bromide and promote the occurrence of ring opening. Using epichlorohydrin as a probe substrate, P-DBTMGH could efficiently catalyze the cycloaddition reaction of the simulated flue gas (15 vol% CO₂ + 85 vol% N₂) without any co-catalyst or solvent, and chloropropene carbonate (CPC) with a selectivity and yield of 99 % and 96 % was obtained, which was better than or equivalent to the results reported previously. Moreover, the theoretical studies deeply understood the synergetic effect of guanidine basic sites and bromide containing binuclear sites on CO₂ activation and ring-opening of epoxides, which provides a better choice for high-value utilization of low partial pressure CO₂ from flue gas.