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 Cs 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 [MeNH]SbS (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, Ca, Mg, and Sr 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 S with Cs, easily exchangeable [MeNH] cations, and the flexible and robust framework of FJSM-SbS with open windows as trappers.