Degussa P-25 TiO2 encapsulated in a SBA-15 mesoporous thin film silica matrix prepared using a block copolymer templating method. The film structure was characterized using small angle X-ray diffraction (XRD), variable angle spectroscopic ellipsometry (VASE), and polarized light microscopy. The photoactivity of the films was assessed using HPLC and UV-vis spectroscopy to study the photodegradation of 2,4-dichlorophenol, an industrial pollutant, in water under 350 nm irradiation. The unoptimized film was found to be approximately half as photoactive as an equivalent dispersion of TiO2 (C) 2004 Elsevier B.V. All rights reserved.