Manganese salophen covalently anchored to amino-functionalized graphene oxide as an efficient heterogeneous catalyst for selective epoxidation

Abstract

Epoxidation of olefins catalyzed by manganese(III) salophen (MnSalop) immobilized on graphene oxide (GO) modified with 3-aminopropyltrimethoxysilane (GO·NH₂) has been reported. Characterization of the solid catalyst by FTIR, DR UV-Vis, FESEM, XRD, elemental scanning mappings, TGA/DTG, BET measurements, and ICP analysis aided in understanding the catalyst morphology. It confirmed that there was no significant demetallation or chemical change in MnSalop-GO·NH₂. The heterogeneous catalyst (MnSalop-GO·NH₂) showed high efficiency in the oxidation of different olefins with H₂O₂ as a green oxygen donor agent assisted by NaHCO₃ as co-catalyst at room temperature. The alkenes were oxidized to their corresponding epoxides with 88–100% selectivity and turnover frequency (TOF) values ranging from 40.7 to 162.8 h⁻¹ in the presence of MnSalop-GO·NH₂ under mild conditions. When supported on GO, MnSalop-GO·NH₂ afforded epoxide yields comparable to those of the corresponding homogeneous analog. The prepared catalyst was selective for most olefins, with a high conversion. In addition, it could be reused four times without any remarkable loss in catalytic performance.