Hybrid organic-inorganic materials were synthesized by sol-gel copolymerization of the N, N-chelate ligand (3-triethoxysilyipropyl) [3-(2-pyridyl)-1-pyrazolyl]acetamide (1) and tetraethoxysilane (TECS). Active solid oxidation catalysts can be obtained by introducing oxodiperoxo molybdenum species MoO((2))(2) into the hybrid sol-gel materials with a ligand-exchange reaction. The molybdenum-containing catalyst, prepared from a sol-gel precursor with relatively large pore volume and high specific surface area, showed a very high stability against leaching of the active species into the liquid phase during the epoxidation of cyclooctene with tert-butyl hydroperoxide ((BuOOH)-Bu-t). (C) 2003 Elsevier Inc. All rights reserved.