Immobilization of dioxomolybdenum(VI) complex bearing salicylidene 2-picoloyl hydrazone on chloropropyl functionalized SBA-15: A highly active, selective and reusable catalyst in olefin epoxidation

• The molybdenum complex anchored to SBA-15 by covalent binding through the ligand.
• High-efficiency catalyst for the selective oxidation of olefins.
• The catalyst exhibited remarkable recyclability for five consecutive cycles.

A novel organic–inorganic hybrid heterogeneous catalyst system was obtained from the reaction of the molybdenum(VI) complex of salicylidene 2-picoloyl hydrazone with mesoporous silica containing 3-chloropropyl groups prepared by a direct synthetic approach involving hydrolysis and co-condensation of tetraethylorthosilicate (TEOS) and 3-chloropropyltrimethoxysilane in the presence of the triblock copolymer P123 as template under acidic conditions. Characterization of the functionalized materials by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), N2 adsorption/desorption, FT-IR and UV–Vis spectroscopy, and thermogravimetric analysis (TGA) reveals that the molybdenum complex is successfully grafted into the pores of the host silica structure. Furthermore, the resulting hybrid material was found to be highly active catalyst in the liquid-phase epoxidation of olefins with t-BuOOH as the oxygen source. Leaching tests and metal analysis of reaction solutions show that the catalytic activity stemmed from the immobilized species, not from the leaching of active species into solution.

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