Nano-sized rutile TiO₂ having the particle size of 1 ~ 5 nm was obtained using MCM-41 and HNO₃ as a sizing agent and a crystal structure determining agent, respectively. Due to its small particle size, the prepared TiO₂ showed larger bandgap than pure bulk rutile TiO₂. The prepared rutile TiO₂ showed higher activity for the photocatalytic oxidation of 2-isopropyl-6-methyl-4-pyrimidinol (IMP) than the bulk rutile TiO₂. A porous anatase TiO₂ was prepared without phase transition to rutile over 600 ℃ through SiO₂ incorporation-extraction procedure.