Reported here are two unprecedented copper-rich open-framework chalcogenides constructed from unusual [Cu-5(SnxM1-x)Se-10] clusters and [(SnxM1-x)(2)Se-6] dimeric linkers (M = In and Ga). The photoresponsive properties in the IR range and the photocatalytic activity for degradation of methylene blue dye of these two isostructural semiconductors were proved to be effectively adjusted by trivalent metal ions in a cluster.