In Situ Cation‐Switched Organometallic Cage Reconfiguration Enables Highly Selective Li⁺ Recognition and Extraction

Biomacromolecular selectivity paradigms, epitomized by the "induced-fit" concept, motivate adaptive supramolecular designs; however, cationic guest-directed morphological responses in metal-coordinated hosts remain inadequately developed. We reveal a dynamic Ag^I-N-heterocyclic carbene (NHC) cage that experiences alkali ion-induced structural metamorphosis triggered by Lewis acid‒base interactions. X-ray crystallographic analysis and independent gradient model (IGM) evidence confirm that these interaction templates have highly ordered architectures exceeding 340 non-H atoms. Competitive affinity assessments exhibit unprecedented Li⁺ discrimination against Na⁺/K⁺ (Li⁺ > Na⁺ > K⁺), outperforming commercial benchmark chelators (e.g., crown ethers and cryptands). Capitalizing on this trait, we fabricated a supramolecular extractant for targeted Li⁺ isolation from both an equimolar Li⁺/Na⁺/K⁺ brine and a high-Mg²⁺ brine (c(Mg²⁺)/c(Li⁺) ≈ 2000/1). Subsequent carbonate-induced reconfiguration reverts the initial metallocage, permitting cyclic utilization. This study deciphers cation-modulated plasticity in coordination architectures and offers a recyclable bioinspired platform for precision ion recognition and extraction.