Swelling Poly (Ionic Liquid)s: Heterogeneous Catalysts That are Superior than Homogeneous Catalyst for Ethylene Carbonate Transformation

Heterogeneous catalysts usually show much lower catalytic activities than homogeneous catalysts due to insufficient dispersion and contact of catalytically active sites to reactants. Efforts have been made to solve this problem during past decades. Herein, we have synthesized a series of poly (ionic liquid)s (PILs), which are well swelled in ethylene carbonate (EC), by polymerization of N-vinylimidazolium ionic liquid monomers with divinylbenzene (DVB). The structure, morphology and swelling property of the PILs were charicreized by ¹³C MAS NMR, FT-IR and SEM. Cyro-SEM showed that the PILs demonstrate a 3D network structure in swelling state which might promote mass transfer and dispersion of active sites. The PILs were utilized in the reaction of 2-(phenylamino) ethanol (2-PAE) and EC and exhibited even better catalytic performance than homogeneous catalyst 1-butyl-3-methyl-imidazolium acetate (BmimOAc). This superior catalytic activity is strongly related to the swelling property and selective absorption behavior of PILs. The absorption behavior was investigated by ¹H NMR analysis of mole ratio of reactants to product inside and outside of PILs in the reaction mixture. It was found that the PILs could enrich reactants and eject products which could accelerate the reaction.