Epoxidation of styrene over Fe(Cr)-MIL-101 metal–organic frameworks

Abstract

Epoxidation of styrene is one of the key reactions in organic synthesis. In this paper, we investigated the effect of different metal ions in MIL-101 metal–organic framework on styrene epoxidation using various oxidants such as air, H₂O₂ and TBHP. For the aerobic epoxidation of styrene, Fe-MIL-101 and Cr-MIL-101 presented good styrene conversion (87.2 vs. 65.5%) and epoxide selectivity (54.4% vs. 37.7%) using air as the oxidant. The styrene epoxidation activity for the different oxidants over Fe-MIL-101 was as follows: air > TBHP > H₂O₂, while that over Cr-MIL-101 showed a different trend: H₂O₂ > air > TBHP. Moreover, the selectivity to styrene oxide for the different oxidants was similar over the two catalysts: TBHP > air > H₂O₂. The study of the effect of various solvents revealed that CH₃CN is the optimal solvent for the aerobic epoxidation of styrene. Furthermore, the catalysts could be reused three times without any significant loss in catalytic activity.