Abstract
90Sr2+ remediation and separation from acidic nuclear waste solution and contaminated seawater have attracted a tremendous amount of public attention but significant challenges remain, mostly originating from the ion-exchange competition induced by a large excess of hard metal cations. Here, we report an atypical oxidic ion-exchange material SZ-4 that can effectively remove 90Sr2+ with record-high removal efficiencies in both acidic solution and seawater, where a distinctive two-step intercalation mechani** is directly visualized by single-crystal structures during an in situ Sr2+ sorption process, revealing a new type of uptake selectivity toward soft cations achieved through collaborative coordination by the oxidic layer and the dimethylamine interlayer as a soft N-donor ligand. These results shed light on designing a new generation of ion-exchange materials for radioisotope decontamination with practical applications.