Mesoporous MCM-41 Materials Modified with Oxodiperoxo Molybdenum Complexes:  Efficient Catalysts for the Epoxidation of Cyclooctene

An organic−inorganic hybrid heterogeneous catalyst system was synthesized by covalently anchoring oxodiperoxo molybdenum complexes [(L−L)MoO(O 2 ) 2 ] (L−L = (3-triethoxysilylpropyl)[3-(2-pyridyl)-1-pyrazolyl]acetamide) onto the mesoporous silica MCM-41 (Si−MCM-41) and aluminosilicate MCM-41 (Al−MCM-41) materials. Characterization of the functionalized materials by powder X-ray diffraction (XRD), N 2 adsorption, and solid-state CP-MAS NMR spectroscopy ( 13 C and 29 Si) demonstrates that the oxodiperoxo molybdenum complexes are grafted successfully into the mesoporous MCM-41 materials. The structures of both the mesoporous materials and the molybdenum complex are preserved during the grafting process. All the hybrid materials are active and truly heterogeneous catalysts for the liquid-phase epoxidation of cyclooctene with t BuOOH as the oxygen source. The catalytic properties (activity and recyclability) of the supported materials can be improved by their further silylation using Me 3 SiCl, which can be explained by the increase of hydrophobicity of the mesoporous surface due to removal of residual Si−OH groups. The modified aluminosilicate MCM-41 materials show higher activities than the corresponding siliceous materials, which might be due to the incorporation of Lewis acidic centers.