There remains a significant need for developing new photocatalytic system to degrade perfluorooctanoic acid (PFOA), a typical persistent organic pollutant. In this study, highly efficient BiOCI nanosheets were prepared by a simple hydrolytic method and employed to decompose PFOA. The UV irradiation BiOCI system decomposed nearly all the added PFOA after 12 h, yielding a defluorination of 59.3% and a minimization ratio of 52.5%. The photocatalytic defluorination rate constant of PFOA on BiOCI was 16.53 mu mol L-1 h(-1), being 1.7 and 14.6 times higher than that on commercial In2O3 and TiO2 (P25), respectively. It was demonstrated the photocatalytic degradation of PFOA on BiOCI mainly followed the direct hole-induced oxidative pathway, and the PFOA degradation was positively correlated with the amount of oxygen vacancies in BiOCI. The oxygen vacancies not only acted as the electron scavengers to suppress the charge recombination, but also favored to bind PFOA tightly on the BiOCI surface through a special monodentate coordination, which is beneficial for the hole oxidation of PFOA. (C) 2017 Elsevier B.V. All rights reserved.