Aiming at developing a highly active photocatalyst to decompose organic compounds under visible light irradiation, we have prepared metal ion doped TiO2 (M-TiO2) by conducting dialysis in sol-gel method. Dialysis leads to the formation of mesoporous materials with surface area larger than 200 m(2) g(-1) but the metal ions should be added into the TiO2 sol at pH 3 in order to avoid their losses during dialysis. Among seven metal ions tested as dopants, Pt-TiO2 and Cr-TiO2 showed higher photocatalytic activity for the degradation of 4-chlorophenol under visible light irradiation. The photocatalytic activity of Cr-TiO2 was strongly affected by the doping amount of Cr ion and the optimal value was evaluated to be 0.68-1.30 atom%. X-ray photoelectron spectroscopy analyses showed the Cr ion was present mainly in Cr(III). The Cr-TiO2 can be used safely for a practical application to remediate environmental contamination instead of expensive Pt-TiO2. (C) 2015 Elsevier B.V. All rights reserved.