Macrocycle-Based Charge-Transfer Cocrystals: From Host-Guest Recognition to Multifunctional Solid-State Materials

Macrocycle-based charge-transfer (CT) cocrystals have recently emerged as a distinctive class of adaptive supramolecular solids that bridge molecular recognition and solid-state functional materials. Unlike conventional CT assemblies, these systems combine host-guest chemistry with intermolecular donor-acceptor interactions, enabling simultaneous regulation of molecular packing, electronic coupling, and excited-state processes. The coexistence of cavity-confined complexation and exo-wall CT assembly, together with the dynamic nature of host-guest interactions, provides unique opportunities for constructing stimuli-responsive materials whose structures and functions can be continuously modulated by external inputs. In this Review, we discuss the fundamental principles underlying the design and construction of macrocycle-based CT cocrystals and highlight how adaptive host-guest recognition governs CT interactions and emergent solid-state properties. Recent advances in vapochromic sensing, molecular separation, photothermal conversion, luminescence modulation, and multifunctional integrated systems are systematically summarized, with particular emphasis on competitive and cooperative structural regulation mechanisms. Finally, we outline current challenges and future directions toward programmable, multicomponent, and application-oriented CT materials. By establishing connections between supramolecular structure, CT behavior, and functional output, this Review aims to provide a conceptual framework for the development of next-generation adaptive molecular solids.