A hybrid mesostructured photocatalyst prepared by using the "postsynthetic modification" approach with the periodic mesoporous organosilicas (PMO) framework and bismuth nitrate was studied. The morphology and structure of the hybrid Bi2SiO5 photocatalyst were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and N-2 adsorption-desorption isotherms. These results of characterization show that the as-prepared Bi2SiO5 keeps a semi-ordered mesostructure as the PMO framework. The results of density functional theory calculations indicated that the conduction band bottom of Bi2SiO5 mainly consist of Bi 6s orbits and O 2p, O 2s, while the valence band top mainly consist of Si 3p. O 2p, and Bi 5d orbits. The as-prepared Bi2SiO5 exhibited efficient photocatalytic activity in the decomposition of a widely used dye, tetraethylated rhodamine (RhB), and phenol in water under the simulative sunlight irradiation. Further, the photocatalytic experiment results show that the hybrid Bi2SiO5 synthesized based on PMO was more efficient than the pure mesoporous Bi2SiO5 in decomposing the organic pollutant, which means the hybrid organic groups dispersed in the PMO framework is advantageous to improve the efficiency of the photocatalyst. (C) 2010 Elsevier B.V. All rights reserved.