Functionally enhanced basic amino acid-based binary organocatalysts based on physical doping for efficient coupling of CO2 with epoxides

Abstract

Amino acids (AAs), as naturally tailored highly functional biomass-based organocatalysts, have great potential to efficiently facilitate the CO₂/epoxide coupling reaction. Herein, we developed a strategy of constructing AA-based binary organocatalysts based on physically doping basic amino acids (BAAs) with polyether guanidinium ionic liquids (PGILs), preparing a series of novel binary BAA/PGIL catalysts. Compared with the current AA-based organocatalysts, the binary BAA/PGIL catalysts were prepared more easily and could catalyze the coupling of CO₂ with structurally diverse epoxides to form the corresponding cyclic carbonates under milder conditions, with superior or comparable activity and lifetime. The enhanced synergy in catalytic activity between BAAs and PGILs was derived from the intermolecular cooperative catalysis among multi-active sites of BAAs and PGILs; in particular, the functional gains caused by polyether-induced hydrogen bond and electrovalent bond blocking-up effects as well as by physical doping-mediated intermolecular hydrogen bonding of binary catalysts played crucial roles. The presented binary BAA/PGIL catalysts represented a new way of efficiently utilizing AA-based organocatalysts, and demonstrated great application potential in the preparation of cyclic carbonates.