Olive-green few-layered BiOI with expanded spacing of the (001) facets and oxygen vacancy is successfully synthesized and characterized. The experimental analysis and theoretical calculation demonstrate that the expanded facets spacing and oxygen vacancy of few-layered BiOI result in enhanced separation efficiency of photoinduced carriers and photon absorption efficiency. Therefore, few-layered BiOI shows much higher photocatalytic activity for CO2 conversion than that of bulk BiOI under visible or near-infrared (NIR) light And the apparent quantum yields (AQY) are 0.14% and 0.02% for few-layered BiOI under 420 and 700 nm monochromatic light irradiation, respectively. These findings deep our understanding of few-layered BiOX (X=Cl,Br,I) photocatalysts, and propose a new route to design high efficient photocatalysts for energy and environmental photocatalysis. (C) 2015 Elsevier B.V. All rights reserved.