Solvent-Free cycloaddition of carbon dioxide and epichlorohydrin catalyzed by surface-attached imidazolium-type poly(ionic liquid) monolayers

Design and synthesis of effective catalysts for the conversion of epoxy compounds to cyclic carbonate under the presence of carbon dioxide molecules is essential for the utilization of carbon dioxide. Herein, we report that the surface-attached imidazolium-type poly(ionic liquid) bearing amine moieties is an efficient catalyst for the conversion of epoxy compound and carbon dioxide to cyclic carbonate. The effect of chemical structure of the synthesized catalyst and the reaction conditions on the catalytic efficiency is systematically studied. The results show that the catalyst with bromide anion can effectively catalyze the reaction under 1.5 MPa carbon dioxide pressure at 120 °C with the catalyst content of 10 mg mL^-1, reaching the conversion rate up to 90 %. Moreover, the synthesized catalyst can be separated from the cyclic carbonate products by centrifugation. The recyclability and reversibility measurements reveal that the decay of the catalytic activity is mainly resulted from the adsorption of the cyclic carbonate products on the catalysts. The catalytic activity of the synthesized catalyst towards conversion of epichlorohydrin and carbon dioxide to cyclic carbonate can be recovered after extraction of the adsorbed cyclic carbonate products.