Hydrothermal synthesis of MSn(OH)6 (M = Co, Cu, Fe, Mg, Mn, Zn) and their photocatalytic activity for the destruction of gaseous benzene

•MSn(OH)6 (MHS, M = Co, Cu, Fe, Mg, Mn, Zn) were synthesized by hydrothermal method.•The preparation condition for complete formation of MHS was identified.•ZnHS and MgHS exhibits significant and stable activity for degradation of gaseous C6H6 and MO solution.•Color MHS samples (M = Co, Cu, Fe, Mn) have no capability to crack benzene ring.

Hexahydroxy-stannates (MSn(OH)6) are promising candidates for photocatalytic degradation of highly stable aromatic compounds. A series of MSn(OH)6 (MHS, M = Co, Cu, Fe, Mg, Mn, Zn) was synthesized by a hydrothermal method in this work. The effects of the hydrothermal temperature, time and the solution pH on the formation of MHS were investigated. The structures, yields, optical properties, and morphologies of the products were then studied. Photocatalytic degradation of gaseous benzene (C6H6) on the prepared MHS was investigated and compared with P25 (TiO2). The results indicate the optimal preparation condition of MHS is performing the hydrothermal treatment at a mild temperature (90–120 °C) in a weak base solution (pH 10–11). Only MgHS and ZnHS exhibit a significant and stable activity for the destruction of C6H6 and the efficiencies are substantially higher than that of P25. The hydroxyl structure accounts for their high performance, which facilitates the formation of the active radicals (OH and O2−) and suppresses the deposition of the stable byproducts. Due to the restriction of the band structures, the degradation of C6H6 cannot be achieved on the colored samples (M = Co, Cu, Fe, and Mn). Based on the radicals analyses results, the degradation route of C6H6 on and the formation route of the stable intermediates on the samples were finally proposed.

Graphical abstractThe effects of the hydrothermal conditions, including temperature, time, and solution pH on the formation of MSn(OH)6 (MHS, M = Co, Cu, Fe, Mg, Mn, Zn) were studied. Only ZnHS and MgHS exhibited a significant and stable photocatalytic activity for the destruction of C6H6, as well as for methyl orange, while the color samples had no capability to open the benzene ring and consequently showed no activity for the destruction of C6H6.Figure optionsDownload full-size imageDownload as PowerPoint slide