Tris-imidazolinium-based porous poly(ionic liquid)s as an efficient catalyst for decarboxylation of cyclic carbonate to epoxide

Abstract

A series of imidazolinium-based porous poly(ionic liquid)s (PILs) with different anions prepared by free-radical copolymerization of an arene-bridged tris-vinylimidazolium salt and divinylbenzene (DVB) were constructed. The as-prepared PILs were characterized by BET, SEM, TEM, TGA and Elemental Analysis (EA), and the results showed that they had plentiful ionic sites, and abundant and stable mesopores. In particular, the density of ionic sites and pore structure of PILs could be controlled by adjusting the content of DVB. Moreover, the PILs were used as efficient heterogeneous catalysts for the decarboxylation of cyclic carbonates to epoxides for the first time. Results showed that the catalytic activity of PILs was positively correlated with the nucleophilicity of the anions in PILs, and PDVB-[PhTVIM]Cl-1 with a chloride anion-enriched skeleton displayed the best catalytic performance. Without any solvent or cocatalyst, PDVB-[PhTVIM]Cl-1 achieved a TOF value of 108.1 h⁻¹ and the yield of butylene oxide of 89.6%, which was even better than the homogeneous IL-based catalysts (TOF value: 8.7 h⁻¹) that had been previously reported. Meanwhile, PDVB-[PhTVIM]Cl-1 also exhibited excellent recyclability and substrate compatibility.