In recent years, chalcogenides have received a lot of attention because of their potential applications as photoelectric material. This work describes the synthesis of the quaternary seleniumstannates Cs 2 MnSnSe 4 (1) and Rb 2 MnSnSe 4 (2) using solvothermal methods. The structure of compound 1 consists of chargebalanced Cs + cation and one-dimensional (1D) anion2À layer. It is noteworthy that the compounds exhibit a strong photocurrent response (ca. 45 μA/cm 2 (1), ca. 80 μA/cm 2 (2)). Moreover, methylene blue (MB) was investigated for its photocatalytic degradation properties. In order to better understand the relationship between optical properties and electronic structure, a theoretical study was conducted.