Mesoporous TiO₂ was prepared using esterification between triblock copolymer (Pluronic P123) and acetic acid, and was applied to the photocatalytic decompositions of 2-isopropyl-6-methyl-4-pyrimidinol (IMP) and cyanide (CN). To increase inorganic-organic interaction which is necessary in synthesis mesoporous material, and hexane. When ethanol was used, a very sharp PSD appeared, but the activity was very low because of its small surface area and pore size which are critical properties in the photocatalytic decompositions of cyanide and IMP, respectively. TiO₂ prepared using acetone gave the very high activity in the cyanide decomposition due to the large surface area. Unlikely, hydrophobic hexane caused large pore size resulting in the increase of the activity of IMP decomposition.