ZnBr2/DMF as simple and highly active Lewis acid–base catalysts for the cycloaddition of CO2 to propylene oxide

• ZnBr2/DMF showed high activity/selectivity for the cycloaddition of CO2 to propylene oxide due to their synergistic effects.
• DMF activated CO2 and ZnBr2 activated propylene oxide.
• Highly active ZnBr2/DMF catalysts are simple and facile available.

It is a great challenge for developing effective and simple catalysts for the cycloaddition of CO2 to epoxides to form cyclic carbonates. In this report, the simple ZnBr2/DMF catalysts were found highly effective to this transformation and a high TOF of 1170 h−1 and 100% selectivity to propylene carbonate were obtained at 150 °C and 3 MPa of CO2. Specially, the catalysts possessed merits of cheapness, effectivity and facile availability, which were very attractive from the viewpoint of industrial applications. Moreover, the effects of various reaction factors, including different Lewis acids and bases used, temperature, CO2 pressure, reaction time and the amount of DMF, were also discussed in detail. Besides, a possible catalytic mechanism for the cycloaddition of CO2 to propylene oxide was proposed.

ZnBr2/DMF catalysts showed a high TOF of 1170 h−1 and 100% selectivity to propylene carbonate for cycloaddition of carbon dioxide with propylene oxide at 150 °C and 3 MPa of CO2, which possessed the merits of simpleness and high activity/selectivity concurrently.Figure optionsDownload as PowerPoint slide