Catalytic epoxidation of propylene over a Schiff-base molybdenum complex supported on a silanized mesostructured cellular foam

A Schiff-base molybdenum complex (MoO2–salen) supported on mesostructured cellular foam (MCF) was initially prepared by an in situ synthesis method under acidic conditions. Following silanization modification, a MoO2–salen@MCF-S sample with improved surface hydrophobicity was obtained. The ligand environment of molybdenum within the samples has been analyzed by Fourier-transform infrared spectroscopy, ultraviolet/visible spectroscopy, and X-ray photoelectron spectroscopy. Furthermore, the textural and structural properties of the corresponding materials have been characterized by nitrogen adsorption–desorption isotherms and transmission electron microscopy. Despite of the presence of fewer MoO2 species, the results showed that MoO2–salen@MCF-S has more active Mo centers than MoO2–salen and MoO2–salen@MCF on the basis of maintaining the mesoporous structure. The catalytic performances of the synthesized samples were assessed in the epoxidation of propylene with tert-butyl hydroperoxide (TBHP) as an oxidant, and the mechanism of propylene epoxidation under MoO2–salen@MCF was given. The prepared MoO2–salen@MCF-S material showed the best epoxidation performance with 1,2-dichloroethane as a solvent and a molar ratio of propylene to TBHP of 10:1 at 120 °C, giving a TBHP conversion of up to 100% after 1 h, with selectivities for propylene oxide and tert-butyl alcohol reaching 94.7% and 84.6%, respectively.