Polyhydroxy Ionic Polymer Catalysts for Highly Selective Cycloaddition of Carbon Dioxide and Epoxides

Graphical New polyhydroxy ionic polymers, poly(1-(2-hydroxyl-ethyl)-3-vinyl-imidazolium bromide)- co -polystyrenes (P[HeVim][Br]- co -PSs), were obtained and used as effective heterogeneous catalysts for the cycloaddition of epoxides and pure CO 2 or 12 vol % CO 2 /N 2 under co-catalyst- and solvent-free condition. Polyhydroxyl groups synergistically promote the ring opening step of epoxide and thus complete cycloaddition selectivity was obtained. New polyhydroxy ionic polymers were designed and prepared to heterogeneously catalyze CO 2 cycloaddition reaction with complete chemoselectivity and up to 99 % yields. Using copolymer of 1-(2-hydroxyl-ethyl)-3-vinyl-imidazolium bromide ([HeVim][Br]) and styrene, the highest yield of propylene carbonate was obtained. And, it is significantly higher than that obtained with the same amount of hydroxy monomer [HeVim][Br] (only 24 % yield), thus showing the concerted promotion effect of polyhydoxyl groups during ring opening of epoxides. The catalyst presented excellent recycling performance (10 cycles). Various terminal cyclic carbonates were synthesized with above 95 % yields. A synergistic function of hydroxyl group as efficient hydrogen bonding donor and bromide anion as nucleophilic agent was put forward.