Recently discovered designs of solid-state molecular solar thermal energy storage systems are illustrated, including alkenes, imines, and anthracenes that undergo reversible [2 + 2] and [4 + 4] photocycloadditions for photon energy storage and release. The energy storage densities of various molecular designs, from 6 kJ mol-1 to 146 kJ mol-1 (or up to 318 J g-1), are compared and summarized, along with effective strategies for engineering their crystal packing structures that facilitate solid-state reactions. Many promising molecular scaffolds introduced here highlight the potential for achieving successful solid-state solar energy storage, guiding further discoveries and the development of new molecular systems for applications in solid-state solar thermal batteries.
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