Rb2CuSb7S12: Quaternary Antimony-Rich Semiconductor Featuring a Three-Dimensional Open Framework and Exhibiting an Intriguing Photocurrent Response.

Metal-rich chalcogenides with unique network architectures are rare but are of considerable interest because of their intriguing physical properties. In this work, a novel quaternary thioantimonate, Rb2CuSb7S12, has been discovered by a facile surfactant-thermal reaction. It crystallizes monoclinic space group P1 (No. 2) and exhibits a unique Sb-rich three-dimensional (3D) [CuSb7S12]2- framework surrounded by charge-compensating Rb+ cations. It is interesting to note that the Cu/Sb ratio of Rb2CuSb7S12 represents the lowest limit in the quaternary A/Cu/Sb/Q (A = alkali metals; Q = chalcogen) system. Moreover, Rb2CuSb7S12 shows rapid response and good reproducibility based on the photoelectrochemical tests. This study opens up opportunities for discovering the desirable physical properties in metal-rich chalcogenides.