A facile solvothermal route is successfully developed to synthesize Bi4O5I2, a novel I-poor bismuth oxyiodide, with hierarchical nanoflake structure. The composition, structure, morphology, formation mechanism, photoabsorption, energy band, and photocatalytic properties of this material are systematically investigated. The results reveal that highly pure Bi4O5I2 can be easily obtained by reacting Bi3+, I-, and OH- at pH values of 6 to 10 under solvothermal conditions, and the formation of such hierarchical structure can be explained by a dissolution-recrystallization mechanism. The as-synthesized 8140512 nanoflakes show a favorable energy band structure (bandgap energy 2.17 eV, conduction band edge potential is more negative than the reduction potential of superoxide radicals), a high specific surface area (38.6 m(2) g(-1)), and a hierarchical micro/nano structures. Thus, they exhibit superior photocatalytic and mineralization efficiency for the degradation of 4-tert-butylphenol (PTBP, a representative alkylphenol) under visible light irradiation, with a reaction rate is 6.8 and 57 times faster than that of BiOI microspheres and N-doped TiO2, respectively. The photogenerated reactive species and degradation intermediates are identified, and possible photocatalytic mechanism is proposed. What's more, the as-synthesized Bi4O5I2 nanoflakes remain stable during the photocatalytic reaction and can be used repeatedly, revealing their promising applications in the treatment of organic wastewaters. (c) 2013 Elsevier B.V. All rights reserved.