Conformationally Adaptive Crown Ether Embedded in a Metal Sulfide for Exceptional Strontium Capture

ABSTRACT Precise conformational control of flexible supramolecular moieties (e.g., crown ethers) in crystalline‐state adsorbents is essential for efficient host–guest recognition. Traditional strategies relying on covalent chemistry are often limited by either tedious synthesis or a sacrifice of conformational flexibility. Here, we introduce a simple non‐covalent anchoring strategy where 18‐crown‐6 (18Cr6) molecules are in‐situ embedded between the interlayer galleries of a perforated thiostannate framework (18Cr6‐SnS) in one‐pot synthesis. This architecture not only ensures ordered alignment of crown ethers but also preserves the intrinsic coordination freedom, thereby enabling exceptional Sr 2+ binding affinity. 18Cr6‐SnS exhibits a record‐high distribution coefficient ( K d = 4.9 × 10 6 mL/g) under neutral conditions and excellent selectivity in simulated acidic high‐level liquid waste, displaying high separation factors ( K d Sr / K d M ) for Cs + (96), Eu 3+ (245), and Ni 2+ (621) in 1 M HNO 3 . Experimental and theoretical analyses reveal that the superior Sr 2+ recognition arises from the conformational adaptability of intercalated crown ethers, coupled with adjustable interlayer spacing. This work establishes a cost‐effective and scalable route to develop advanced adsorbents by synergizing host materials with flexible supramolecular receptors for critical energy and environmental applications.