ZnBr ₂-based choline chloride ionic liquid for efficient fixation of CO ₂to cyclic carbonate

(Chemical Equation Presented) In this work, ZnBr ₂-based choline chloride (CH) was first investigated to catalyze the synthesis of cyclic carbonates from CO ₂ and epoxides under solventless conditions. It was demonstrated that ZnBr ₂-based CH was very efficient and selective. Under the optimum reaction conditions, 99% yield of propylene carbonate was achieved. The catalyst can be reused five times without loss of catalytic activity. It was proved to be very active in a variety of terminal epoxides with CO ₂. In addition, a synergistic catalytic mechanism by Zn ²⁺ and -OH was proposed.