Mesoporous anatase TiO2 has been successfully prepared in water at lower temperatures than 90 degrees C. Firstly, amorphous TiO2 gels were prepared by conventional sot-gel method at room temperature with tetrabutyl titanate as precursor, and then TiO2 gels were directly put into water at temperatures of 50-90 degrees C for 0.5-10h to form mesoporous anatase TiO2. The as-prepared mesoporous TiO2 was characterized by XRD, TEM, FTIR, Raman, UV-vis DRS, DSC-TGA, and XPS. The results showed that mesoporous anatase TiO2 contained some organic residuals, the mean size of the TiO2 nanocrystals was in the range of 3.5-5.4 am, and their BET specific surface areas were in the range of 235-345 m(2) g(-1). The photocatalytic activity of as-prepared TiO2 was obviously higher than those of the commercial TiO2 (P25) and TiO2 calcined at 450 degrees C for 3 h under UV or visible light irradiation. (C) 2015 Elsevier Ltd. All rights reserved.