Modified stannous sulfide nanoparticles with metal-organic framework: Toward efficient and enhanced photocatalytic reduction of chromium (VI) under visible light.

Novel metal-organic framework/stannous sulfide (MIL-53(Fe)/SnS) nanocomposite photocatalysts were successfully synthesized by a one-step deposition process. The structure, composition and optical properties of the MIL-53(Fe)/SnS composite were systematically characterized by the X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, Fourier transform-infrared spectroscopy, UV-vis diffuse reflection spectroscopy and photoluminescence analysis. The photocatalytic performance of MIL-53(Fe)/SnS composite has been evaluated in the reduction of chromium (VI) under visible-light irradiation. Compared with pure MIL-53(Fe) and SnS, the MIL-53(Fe)/SnS composite exhibited enhanced photoreduction capability of chromium (VI) due to the strengthened absorption in the visible region, higher electron-hole separation rate and larger specific area. The MIL-53(Fe)/SnS composite with MIL-53(Fe) adding of 15 mg displayed optimal chromium (VI) reduction rate of 0.01878 min, which was about 7.5 and 5.2 times than pure MIL-53(Fe) and SnS, respectively. The active species superoxide radical (O), electron(e) and hole(h) are essential toward chromium (VI) reduction. Lastly, a possible photocatalytic mechanism is proposed.