Here we report the aqueous photodegradation of 4-chlorophenol under visible light (wavelength > 400 nm) with three kinds of mesoporous molecular sieves (MCM-41. MCM-48, and SBA-15) incorporated with Cr and TiO2 (TiO2)/Cr-MS). The Si/Cr atomic ratios in the synthesized materials are 80, 40 and 20, respectively. These materials are characterized with BET surface area, pore size distribution, X-ray diffraction (XRD), ultraviolet-visible light (UV-vis) spectra, and temperature-progammed reduction (TPR). UV-vis and TPR results indicate that the Cr is present as Cr6+ in all Cr-MS and TiO2/Cr-MS samples. The TPR results further indicate that an Si-O-Cr-O-Si bond structure is formed in the MCM-41 matrix, bulk Cr oxide exists Outside the MCM-48 matrix, and Cr interacts mainly with silica on the surface of SBA-15. The incorporation of Cr extends the light absorption edge of TiO2/Cr-MS to 550 nm. The activities of TiO2/Cr-MS with different molecular sieves are compared for aqueous photodegradation of 4-chlorophenol under visible light. It is found that the molecular sieve plays an important role in photocatalyst activity and that MCM-41 is the support producing the best photocatalyst. The interaction of Cr6+ and TiO2 allows for a special transition under visible light, Cr6+ = O2- -> Cr5+ - Ot-. and is essential for the activity of a photocatalyst under visible fight. (c) 2005 Elsevier Inc. All rights reserved.