Light-Controlled Functions with Metal–Organic Capsules: From Guest Release to Catalysis, Separation, and Molecular Transport

ConspectusLight offers a clean and precise means to control chemical processes. These advantages have opened the door to the development of dynamic host-guest systems, whose functions can be turned on or off with specific wavelengths. Over recent years, we have developed a suite of light-responsive metal-organic capsules that use azobenzene photoisomerization to direct functions that include reversible guest encapsulation, selective molecular separations, controlled catalysis, and directional mass transport. These capsules, assembled via subcomponent self-assembly, incorporate azobenzene-based ligands that undergo photoinduced <i>trans</i>-<i>cis</i> isomerization. This reversible switching induces cage disassembly or changes in host-guest binding, enabling light to act as an external signal to modulate activity.In this Account, we summarize five key studies that trace the evolution of this platform, from basic molecular recognition and guest release to complex, multicomponent systems capable of energy transduction and spatial molecular control. We describe (i) the design and mechanistic studies of phototriggered guest release using a tetrahedral Zn₄L₄ cage; (ii) the use of an architecture built on this initial work to purify progesterone selectively from mixed steroidal systems; (iii) light-gated catalytic activation using a caged perrhenate system; (iv) selective lithium ion extraction using photoswitchable sandwich architecture; and (v) a Maxwell's Demon-inspired setup that achieves directional molecular pumping across centimeter-scale distances. Collectively, these studies demonstrate how light-responsive metal-organic capsules can be programmed to perform diverse chemical functions, including guest release, selective separations, catalysis, ion extraction, and directional transport. This body of work establishes a platform for the future development of integrated, autonomous, and energy-efficient light-driven supramolecular technologies.