Adaptive Co‐Crystals with Switchable Host‐Guest Stoichiometry for Dynamic Regulation of Photoluminescence

Abstract The development of photoluminescence materials with tunable properties through structural and functional modifications remains a fascinating yet challenging task. In this work, the concept of adaptive co‐crystals featuring switchable host‐guest stoichiometry within the realm of pillararene‐based supramolecular chemistry is proposed. This strategy allows for the rational design of a diverse range of through‐space charge‐transfer co‐crystals, enabling dynamic modulation of photoluminescence in the solid state. Experimental and theoretical findings unveil two distinct phases within each set of co‐crystal architectures, characterized by different donor/acceptor stoichiometric ratios as well as molecular packing modes. Notably, these co‐crystalline phases undergo vapor‐induced stoichiometry switching and structural interconversion, resulting in unique charge‐transfer transition states and enabling reversible control over photoluminescent behavior. Particularly, this dynamic modulation of the cavity apertures, driven by stoichiometric variation, facilitates highly selective capture and release of 1‐bromoalkane under mild conditions. The present study highlights the potential application of vapor‐mediated co‐crystals with switchable stoichiometry as a supramolecular strategy for modulating the intrinsic characteristics of intermolecular donor–acceptor materials.