Mesoporous titania-silica mixed oxides with covalently bound 3-chloropropyl, 3-acetoxypropyl, and N,N-dimethyl-3-aminopropyl groups were prepared from the corresponding alkyltrimethoxysilane and tetramethoxysilane using a sol-gel process and ensuing low temperature supercritical extraction with CO2. The aerogels were characterized by thermal analysis, N-2 and NH3 adsorption, infrared spectroscopy, and Si-29 and C-13 NMR spectroscopy. The modified aerogels showed reduced thermal stability compared to the unmodified titania-silica aerogel, Si-C bond breaking was detected already around 150 degrees C. Si-29 MAS NMR measurements indicated covalent incorporation of the modifying group. DRIFT and NMR measurements confirmed the incorporation of 3-acetoxypropyl and N,N-dimethyl-3-aminopropyl groups and indicated the partial hydrolysis of 3-chloropropyl group to the corresponding alcohol. The activity in the epoxidation of cyclohexene and cyclohexenol with tert-butylhydroperoxide was significantly higher for 3-acetoxypropyl- and N,N-dimethyl-3-aminopropyl-modified catalysts than for the unmodified aerogel. Cyclohexenol oxide selectivity with the N,N-dimethyl-3-aminopropyl-modified catalyst was 94% at 91% peroxide conversion. The new aerogels are compared to other known Ti-and Si-containing epoxidation catalysts, including titania-silica mixed oxides modified by apolar functional groups. (C) 2000 Academic Press.