It is imperative yet challenging to efficiently sequester the 137Cs+ ion from aqueous solutions because of its highly environmental mobility and extremely high radiotoxicity. The systematical clarification for underlying mechanism of Cs+ removal and elution at the molecular level is rare. Here, efficient Cs+ capture is achieved by a thioantimonate [MeNH3]3Sb9S15 (FJSM–SbS) with high capacity, fast kinetics, wide pH durability, excellent β and γ radiation resistances, and facile elution. The Cs+ removal is not significantly impacted by coexisting Na+, K+, Ca2+, Mg2+, and Sr2+ ions which is beneficial to the remediation of Cs+-contaminated real waters. Importantly, the mechanism is directly illuminated by revealing an unprecedented single-crystal to single-crystal structural transformation upon Cs+ uptake and elution processes. The superior Cs+ removal results from an unusual synergy from strong affinity of soft S2– with Cs+, easily exchangeable [MeNH3]+ cations, and the flexible and robust framework of FJSM–SbS with open windows as trappers.

Thiol–amine solvent mixtures have been widely applied in the solution processing of binary chalcogenide thin films due to their excellent ability to dissolve various bulk binary chalcogenides. However, application of this solvent system in preparing new crystalline chalcogenidometalates has not been explored. In this work, by using a thiol–amine solvent mixture of n-butylamine (BA) and 1,2-ethanedithiol (EDT) as the reaction medium and protonated piperazine (pip) cation as the template, we synthesized a series of new chalcogenidoarsenates with structures ranging from discrete clusters to two-dimensional layers, namely, [pipH2]­[pipH]­[AsS4] (1), [pipH2]­[pipH]­[As­(Se0.4S0.6)4] (2), [pipH2]2[pipH]2[In2AsIII 2AsV 2S13.3(S2)0.7] (3), [pipH2]2[pipH]2[In2AsIII 2AsV 2S10.2Se3.1(Se2)0.7] (4), [pipH2]0.5[AsS­(S2)] (5), [pipH2]0.5[AsS2] (6), [pipH]2[AgAsS4] (7), [pipH2]1.5[GaAsIIIAsVS7] (8), and Cs2[pipH]2[InAs6S12]Cl (9). Particularly, compounds 3, 4, and 8 contain mixed-valent AsIII and AsV ions in their discrete clusters and one-dimensional chain. In addition, compound 5 could thermodynamically transform to compound 6 with increasing reaction temperature, which may be attributed to the thermodynamically unstable S–S species in the chains of 5. The BA–EDT solvent mixture was crucial to the synthesis of these compounds, since no title crystals can be prepared by replacing the BA–EDT solvent mixture with other conventional solvents or removing one component of the BA–EDT solvent mixture from the reaction system. Our research demonstrates that thiol–amine solvent systems could be promising reaction media for growing novel crystalline chalcogenidometalates.

An open-framework chalcogenidoantimonate, namely, [CH NH ] Ga SbS S O H (1), has been solvothermally synthesized and structurally characterized. Interestingly, 1 showed Ni ion-exchange properties and wide pH resistance, with a maximum exchange capacity of 76.9 mg g . To the best of our knowledge, this is the first example of amine-directed three-dimensional (3D) heterometallic chalcogenidometalates for highly selective Ni ion capture with a high distribution coefficient (K =1.65×10 mL g ).