Switchable coadsorption and separation for elimination/partitioning of Cs + and Sr 2+ is achieved by pH-controlled ion exchange using a potassium thioantimonate K 2 Sb 4 S 7 •2H 2 O (SbS-1K) with fantastic pH durability from diluted NaOH (pH 12) to concentrated HCl (3 m). At pH 6, SbS-1K exhibits ultrafast adsorption kinetics (R ≈ 90% in 2 min for Cs + and 20 min for Sr 2+ ) and high removal rates (R ≈ 98-99%) at equilibrium for both Cs + and Sr 2+ . At pH 2, the Sr 2+ adsorption is inhibited by H + with a great loss in R Sr to 11.18%, whereas the R Cs remains at 96.99%, contributing to a top-ranked separation factor SF Cs/Sr of 256. The SbS-1K-filled ion exchange column can be switched between the eliminating (R Cs > 99.91%; R Sr > 98.19%) and separating (R Cs > 98.99%; R Sr ≈ 0±3%) modes for treating continuous flow with a variation from pH 6 to pH 2 or vice versa. The SbS-1K/PTFE membrane exhibits coadsorption and separation effects for filtration of low concentrated mixed Cs + and Sr 2+ solution (1 ppm for each), even at an ultrafast vacuum filtration speed (30 mL min -1 ). Combined with easy synthesis and high β/γ irradiation resistance, SbS-1K represents a new-concept bifunctional exchanger with discriminating intelligence for equipment innovation.

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Deep investigations on the synthetic and structural chemistry of heterometallic chalcogenidostannates bear fundamental significance for the establishment of the structure–property relationship that would offer guidance on the functional material innovation. Presented here are four ammonium- and/or alkylammonium-directed M–Sn–Q (M = Zn, Cd; Q = S, Se) compounds, namely, [NH4]7[H3O]3Zn4Sn4S17 (1), [NH4]5[(CH3)2NH2]Zn4Sn5S17 (2), [CH3CH2NH3]22Zn16Sn12Se51(H2O)4·16H2O (3), and [NH4]2CdSnSe4 (4). All four compounds were synthesized in deep eutectic solvents (DESs) or ethylamine aqueous solution, both of which function simultaneously as reaction media and structure-directing agents. Compound 1 consists of discrete P1-[Zn4Sn4S17]10– clusters templated by mixed [NH4]+/[H3O]+ cations. In compound 2, such P1 clusters are bridged by Sn4+ ions in a 4,4-connection mode to form a [Zn4Sn5S17] n 6n– framework with three types of cavities (I–III) varying in size. The two smaller cavities (I and II) accommodate NH4 + while the larger one(III) is occupied by [(CH3)2NH2]+, reflecting the rational size-dependence of cations on cavities. Compound 3 features an [Zn16Sn12Se51(H2O)4] n 22n– open framework constructed from the 4,3-connection of P1-[Zn4Sn4Se17]10– clusters and {Zn(H2O)}2+ bridges. This linkage mode contributes to a large cage-like subunit (inner dimension: 21.99 × 9.06 Å2) and therefore an ultrahigh porosity that are occupied by [CH3CH2NH3]+ cations and water molecules (volume fraction: 57.7%). Compound 4 exists as a stacking of [CdSnSe4] n 2n– chains, which are composed of alternatively arranged {CdSe4} and {SnSe4} tetrahedra, in combination with [NH4]+ cations as both charge-compensating and space-filling agents. Detailed synthetic, structural, and topological analyses were performed on these solid materials, coupled with extensive investigations on their optical and thermal properties. Compound 3 exhibits an efficient Sr2+ adsorption performance, featuring ultrafast kinetics (94.69% in 5 min), high removal rate (98.57% in 20 min) at equilibrium, and high capacity (104.17 ± 23.53 mg g–1).