Nanostructured molybdenum oxides are promising materials for energy storage, catalysis, and electronic-based applications. Herein, we report the synthesis of MoO3–x nanosheets (x stands for oxygen vacancy) via an environmentally friendly liquid exfoliation approach. The process involves the reflux of the bulk α-MoO3 precursor in water at 80 °C for 7 days. Electron microscopy and atomic force microscopy show that the MoO3–x nanosheets are a few nanometer thick. MoO3–x nanosheets exhibit near infrared plasmonic property that can be enhanced by visible light irradiation for a short time (10 min). Photocatalytic activity of MoO3–x nanosheets for organic dye decolorization is examined using two different dyes (rhodamine B and methylene blue). Under visible light irradiation, MoO3–x nanosheets make a rapid decolorization for the dye molecules in less than 10 min. The simple synthesis procedure of MoO3–x …