Robust and Flexible Thioantimonate Materials for Cs+ Remediation with Distinctive Structural Transformation: A Clear Insight into the Ion-Exchange Mechanism

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.