[en] In this work, uniform BiOCl microspheres were used as self-sacrificed template to construct Bi₂O₃/BiOCl heterojunctions by a simple alkaline treatment method. Details of structure and chemical properties were carefully characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectroscopy, and Brunauer–Emmett–Teller techniques. The results indicated that BiOCl microspheres composed of numerous nanosheets transformed to rod-like Bi₂O₃ nanostructures during the alkaline treatment, which resulted in strong visible-light absorption. The as-obtained Bi₂O₃/BiOCl heterojunctions exhibited remarkably enhanced photocatalytic performance for the degradation of methyl orange (MO) under visible-light irradiation, which was ~1.2 and 2.5 times as that of pure BiOCl and Bi₂O₃, respectively. The formation of Bi₂O₃/BiOCl heterojunctions facilitated the transfer and separation of photogenerated charge carriers which was further confirmed by the photocurrent measurement and photoluminescence spectra results. The finding reported here offers a valid in situ route for constructing heterojunction photocatalysts to effectively decompose the organic pollutants in aqueous solution.