Bifunctional Boron Phosphate as an Efficient Catalyst for Epoxide Activation to Synthesize Cyclic Carbonates with CO2.

Development of inexpensive, easily prepared, non-toxic, and efficient catalysts for the cycloaddition of CO2 with epoxides to synthesize five-membered cyclic carbonates is a very attractive topic in the field of CO2 transformation. In this work, we conducted the first work on the cycloaddition of CO2 with epoxides to produce cyclic carbonates catalyzed by a binary catalyst system consisting of KI and boron phosphate (BPO4 ), which are both inexpensive and non-toxic, and various corresponding cyclic carbonates could be produced with high yields (93-99 %) at 110 °C with a CO2 pressure of 4 MPa under solvent-free conditions. In the BPO4 /KI catalyst system, BPO4 , a Brønsted and Lewis acid hybrid, played the role of activating the epoxy ring through the formation of hydrogen bonds with Brønsted acidic sites and the interaction with Lewis acidic sites simultaneously, and thus enhanced the activity of KI for the cycloaddition of CO2 with epoxides significantly. Additionally, the activity of the BPO4 /KI catalyst system showed no noticeable decrease after being reused five times, indicating that the BPO4 was stable under the reaction conditions.