Copper-Rich Framework Sulfides: A₄Cu₈Ge₃S₁₂ (A = K, Rb) with Cubic Perovskite Structure

Two copper-rich open-framework sulfides, K4Cu8Ge3S12 (1) and Rb4Cu8Ge3S12 (2), have been synthesized under solvothermal conditions. Compounds 1 and 2 are isostructural and contain icosahedral [Cu8S12]16− clusters as basic building blocks. These clusters are primitive cubic packed and connect to one another by discrete Ge4+ ions to generate 3D copper-rich Cu−Ge−S framework and form 3D channels along ⟨100⟩ directions where the alkali metal cations reside. These two open-framework sulfides crystallize in cubic perovskite structure.