TiO₂-loaded mesoporous materials were prepared by sol-gel method. Mesoporous materials suppressed the phase transformation of TiO₂ from anatase to rutile and increased the bandgap of TiO₂, which was explained in terms of the quantum size effect. Several kinds of nano-sized TiO₂, with particle sizes of 5 ~ 20 nm, were obtained through the removal of the mesoporous materials by etching in 2 M NaOH or the calcination under air condition. They showed good activities in the photocatalytic oxidation of 2-isopropyl-6-methyl-4-pyrimidinol.