Enhancing selectivity of cation exchange with anion receptors

Abstract

We introduce a new supramolecular strategy where an anion receptor modifies the selectivity ligands for cations. This is demonstrated by combining the classic anion receptor calix[4]pyrrole (C4P) and a phenolic ligand, which leads to remarkable enhancement in selectivity for Cs⁺ over Na⁺. Crystal structures and molecular simulations confirmed the persistent formation of ion-pair C4P–Cs⁺–phenolate complexes, while the smaller Na⁺ ion cannot efficiently interact.