Fabrication of MOF-derived tubular InO@SnInS hybrid: Heterojunction formation and promoted photocatalytic reduction of Cr(VI) under visible light.

Tubular InO@SnInS hierarchical hybrid photocatalyst was firstly fabricated by a two-step method. The morphology and composition were characterized by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The XRD results show that the obtained InO microtubes were highly crystallized, while the SnInS flakes prepared at low temperature were poorly crystallized. The SEM image of the hybrid shows that numerous SnInS nanoflakes were assembled over the surface of InO microtubes. InO served as dispersing-templates have reduced the agglomeration of SnInS flakes. Meanwhile, the heterojunctions formed at the interfaces between InO and SnInS could facilitate the interfacial charge transfer, as well as promote the photocatalytic activity of the hybrid. In the treatment of Cr(VI)-containing wastewater, the InO@SnInS hybrid not only exhibited strong adsorption ability, but also showed remarkably enhanced photocatalytic activity compared with pure SnInS. The photocatalytic reaction constant k for InO@SnInS was approximately 2.54 times higher than that of SnInS. The efficient activity of this hybrid photocatalyst should be ascribed to the promoted separation efficiency of electron/hole pairs, which was proved by the following three-dimensional excitation-emission matrix fluorescence spectra (3D EEMs), photocurrent responds, and EIS characterizations.