The novel photocatalyst of M-doped TiO2 nanoparticles in TUD-1 siliceous mesoporous material, M-TiO2-TUD-1 (M = Cr or V), was synthesized in one-pot highly-controlled synthesis procedure. Three samples were prepared for this study; the first prepared with Si/Ti ratio of 2.5 without any dopant. In the second and the third; 2 wt. % of titanium were replaced by chromium and by vanadium, respectively. The obtained materials were characterized by means of elemental analysis, N-2 sorption measurements, x-ray powder diffraction (XRD), UV-Vis and Raman spectroscopy, scanning electron microscopy (SEM) as well as high resolution transmission electron microscopy (HR-TEM). The characterization results showed that all samples contain nanoparticles of TiO2 (anatase phase, average size of 4-5 nm) embedded in the mesopores of the amorphous siliceous TUD-1, with a co-existence of Cr6+ or V5+ ions. The prepared materials were used to photocatalyze the decolourization of methyl orange (MO) in aqueous medium as a model compound under the illumination of visible light (lambda = 420 nm). The photocatalytic performance of TiO2-TUD-1 mesoporous material showed higher decolourization rate than the commercial TiO2. The performance of TiO2-TUD-1 was highly improved by doping with Cr and V. The order of the catalytic activity of the applied photocatalysts was Cr-TiO2-TUD-1 > V-TiO2-TUD-1 > TiO2-TUD-1 > TiO2 Hombikat. The effect of the support, i.e. TUD-1 versus MCM-41 was also investigated, the performance of Cr-TiO2-TUD-1 was two times better than Cr-TiO2-MCM-41. (C) 2014 Elsevier B.V. All rights reserved.