Amino Acid Anion Paired Mesoporous Poly(ionic liquids) as Metal-/Halogen-Free Heterogeneous Catalysts for Carbon Dioxide Fixation

Abstract

Carbon dioxide (CO2) fixation into high-value-added chemicals over eco-friendly heterogeneous catalysts has attracted a long-lasting concern but remains a huge challenge. Herein, we report the efficient metal-/halogen-/solvent-/additive-free heterogeneous CO2 coupling with aziridines catalyzed by amino acid anion paired mesoporous poly(ionic liquids) (AA-MPILs). A combination of solvothermal synthesis and ion exchange facilely regulated the cations and anions of framework ionic moieties, enabling multifunctional active sites including an acidic carboxyl group, a basic amino group, and a carboxylate as a halogen-free nucleophile with superior leaving ability. The amino group tethered cation and carboxyl groups in the anions promoted the CO2 adsorption capacity. High yield (>95%) and regioselectivity (>99% for 5-substituted oxazolidinone) and remarkable reusability were reached in the CO2 cycloaddition with aziridines under mild conditions. The catalyst was also highly active in the coupling of CO2 with epoxides for the synthesis of cyclic carbonates.