A novel bismuth oxychloride (BiOCl) was synthesized by a hydrolysis method. The powder sample was characterized by X-ray diffraction, field emission scanning electron microscope and UV-vis spectrophotometer. The layered compound BiOCl was the first oxyhalide to be used as a photocatalyst. The prepared material has an optical indirect band-gap of 3.46 eV. For its photocatalytic reactivity, the methyl orange (MO) dye degradation was chosen to be investigated. In a comparison of a three-cycle measurement of BiOCl with that of TiO2 (P25, Degussa), it was found that BiOCl had better performance than P25 at every recycle. The calculated electronic structure of BiOCl confirms that it has an indirect band-gap, and the Cl 3p and Bi 6p states dominate the highest occupied molecular orbitals (HOMO) and the lowest unoccupied orbitals (LUMO), respectively. The open crystal structure and indirect optical transitions of BiOCl play important roles in its excellent photocatalytic activity. (c) 2006 Elsevier B.V. All rights reserved.