Open-framework chalcogenides with ion-exchange capacity are promising materials for removing hazardous heavy-metal ions and for capturing radioactive Cs+. However, research on the exchange mechanism is limited, especially for the framework chalcogenides that have multiple bridging anions. Generally, open framework chalcogenides that have multiple bridging anions at the window or wall of the channels are rigid during the ion-exchange process. We show here that microporous sulfides with it mu(3)-S2-(where mu(3) = triple bridging mode) at the windows exhibit framework flexibility upon ion exchange. Three new microporous sulfides Na4Cu8Ge3S12 center dot 2H(2)O (1), Na-3(Hen)Cu8Sn3S12 (where en = ethylenediamine) (2) and (dap)(2)(Hdap)(4)Cu8Ge3S18 (where dap = 1,2-diaminopropane) (3) were synthesized under solvothermal conditions. Compounds 1 and 2 contain a copper-rich framework composed of icosahedral [Cu8S12](16-) units linked via monomeric GeS44- or SnS44- tetrahedral units, whereas compound 3 features an expanded framework composed of icosahedral [Cu8S12](16-) units interconnected with dimeric Ge2S64- units. These compounds exhibit unusual ion-exchange properties. Specifically, the frameworks of 1 and 2 (with mu(3)-S at the small windows) show "breathing action" upon ion exchange of K+ or Rb+, which have relative large sizes, and compound 3 exhibits framework flexibility upon Cs+ ion exchange with both space group and channels changed.