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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 (C 6 H 6 ) on the prepared MHS was investigated and compared with P25 (TiO 2 ). 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 C 6 H 6 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 O 2 − ) and suppresses the deposition of the stable byproducts. Due to the restriction of the band structures, the degradation of C 6 H 6 cannot be achieved on the colored samples (M = Co, Cu, Fe, and Mn). Based on the radicals analyses results, the degradation route of C 6 H 6 on and the formation route of the stable intermediates on the samples were finally proposed. [ABSTRACT FROM AUTHOR]