Mesoporous anatase TiO_2 spheres with high surface area(119 m^2g^(-1)) were successfully synthesized via a facile and green template-free method. The prepared TiO_2 was characterized by X-ray diffraction(XRD),N_2 adsorption, scanning electron microscopy(SEM), transmission electron microscopy(TEM) and UV–vis absorbance spectra. It was found that the prepared TiO_2 is characterized by pure anatase phase, which shows uniform spheres and has a typical mesostructure with a high specific surface area and a large pore volume. The effects of complexant(acetylacetone) amount, crystallization temperature and calcination temperature were also investigated. Based on the results, a sketch for the preparation of mesoporous TiO_2 was proposed. First, complex formed between tetrabutyl titanate and acetylacetone in ethanol. After introduction of aqueous of ammonia sulfate and urea, hydrolysis of tetrabutyl titanate would occur slowly,and sol of TiO_2 was formed. Then, crystallization proceeded under hydrothermal conditions. Calcination process favored the formation of bigger TiO_2 crystal through combining of the small crystals in TiO_2.This led to the formation of bigger mesopores between TiO_2 crystals. Photocatalytic activity of the prepared TiO_2 was evaluated by decomposition of methyl orange.
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