Active solid oxidation catalysts can be obtained by incorporating dioxomolybdenum(VI) species derived from MoO2Cl2(OPMePh2)(2) into silica matrices via a sol-gel method. The supported catalyst has been characterized by elemental analysis, XRD, N-2-physisorption, FT-IR, FTR-aman, UV-vis and solid-state MAS NMR spectroscopy, and a pathway for the reaction between MoO2Cl2(OPMePh2)(2) and tetraethoxysilane (TEOS) is suggested. The molybdenum catalyst was tested in the epoxidation of cyclohexene in the presence of tert-butyl hydroperoxide (TBHP). The conversion of cyclohexene and the selectivity to the epoxide were very high and increased further on raising the reaction temperature. (c) 2005 Elsevier B.V. All rights reserved.