Conjugate acid-base bi-functional polymeric ionic liquids (CAB-PILs) as efficient catalysts for CO₂ capture and subsequent glycidol cycloaddition reaction

Conjugate acid-base bi-functional PILs (CAB-PILs) with carboxylate and carboxyl branches were synthesized and used as catalysts for the cycloaddition reaction of glycidol with CO₂. Two functional ionic monomers, 3-(carboxymethyl)-1-vinyl-1H-imidazol-3-ium chloride (CEImCl) and 2-(1-vinyl-1H-imidazol-3-ium-3-yl) acetate (CCIm), were introduced into the CAB-PILs skeleton. In this case, we proved the excellent characteristics of the catalyst containing both Lewis base and Bronsted acid sites for converting CO₂ to cyclic carbonate under mild conditions. The catalyst showed good reusability and remained excellent activity after five reaction cycles. Combined with XPS, FTIR and DFT calculations, it is proved that the CCIm ionic monomer not only play the role of CO₂ absorption center, but also has synergistic effect with CEImCl in CAB-PILs to promote cycloaddition reaction.