Molecular‐Gate Strategy for Solid‐State Selective Recognition of Dioxane Isomers via Reversible Host–Guest and Charge‐Transfer Modulation

ABSTRACT Achieving highly selective molecular recognition in the solid state remains a major challenge in supramolecular chemistry. Herein, we introduce a molecular‐gate strategy that dynamically amplifies intrinsic solid‐state recognition selectivity in a macrocyclic host–guest system. A perethylated leaning pillar[6]arene (EtLP6) accommodates both 1,3‐ and 1,4‐dioxane isomers in the solid state, exhibiting only modest inherent selectivity. Remarkably, incorporation of an independent, reversible, charge‐transfer‐active molecular gate, tetrafluoroterephthalonitrile (TFTN), converts this weak preference into highly selective recognition through competitive binding and solid‐state reorganization. The stronger‐binding 1,4‐dioxane displaces TFTN to open the gate and form a host–guest complex, whereas the weaker‐binding 1,3‐dioxane stabilizes a gated CT assembly that suppresses complexation. This gate‐controlled process couples selective recognition with switchable CT interactions, enabling vapochromic discrimination of dioxane isomers. Furthermore, sequential competitive binding enables dynamic regulation of solid‐state assemblies, including room‐temperature‐controlled guest release, and host recyclability. This work establishes molecular gating as a general and conceptually simple strategy for regulating selectivity and functionality in solid‐state macrocyclic host–guest systems.