In this study nanoporous TiO2 photocatalysts with high crystallinity and large surface areas (213.6-586.4 m(2)/g) [CnTiO2-m] were synthesized at room temperature by sal-gel processing and ultrasound irradiation. A cationic surfactant [CH3(CH2)(n)(CH3)(3)Br; C(n)TAB] and tetra-n-butyl titanate (TBOT) were used as the surfactant and titanium precursor, respectively. The prepared CnTiO2-m (m: ultrasound irradiation time, min) samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and Brunauer-Emmett-Teller (BET) surface areas analysis. The photocatalytic activity was evaluated by the photocatalytic oxidation of the azo dyes reactive black 5 (RB 5) and rhodamine B (Rho B) in air. The fastest degradation rate ([k]) was 2.603 h(-1) (C11TiO2-40), which was 3.3 times faster than that of P25 ([k] = 0.791 h(-1)), 6.4 times faster than that of TiO2-40 nm ([k] = 0.409 h(-1)) and 5.5 times faster than that of TiO2-5 nm ([k]= 0.471 h(-1)). The high photocatalytic activity of CnTiO2-m is attributed to its large surface area, well-crystallized anatase and anatase/brookite nanostructure. The recycling of the photocatalytic activity of the C11TiO2-40 was found to be high and the decolorization rate after 15 cycles was 93.1% of the initial value, These results indicate that CnTiO2-m have great potential for use as a photocatalyst. (C) 2013 Elsevier B.V. All rights reserved.