Cyclic carbonates synthesis from epoxides and CO2 over metal-organic framework Cr-MIL-101

The catalytic performance of the metal-organic framework Cr-MIL-101 in solvent-free coupling of CO2 and epoxides to produce cyclic carbonates has been explored at both high-pressure (100 atm CO2) and low-pressure (8 atm CO2) conditions in the temperature range of 25-120 degrees C. The presence of tetrabutylammonium bromide as co-catalyst was found to be crucial for the formation of the cyclic carbonates at mild reaction Conditions (8 atm CO2, 25 degrees C). The yield of the styrene carbonate attained 95% at 98% substrate conversion after 48 h. Cycloaddition of CO2 to propylene oxide gave propylene carbonate with 82% yield at 91% conversion after 24 h. Heterogeneous nature of catalysis was proved by hot catalyst filtration test, indicating no leaching of active chromium species. However, a deterioration of the catalytic properties occurred after catalyst recycling due to pores blockage with the reaction products and gradual degradation of the MIL-101 structure. (C) 2012 Elsevier Inc. All rights reserved.