Storing energy with molecular photoisomers

Summary Some molecular photoisomers can be isomerized to a metastable high-energy state by exposure light. These molecules then thermally or catalytically converted back their initial state, releasing heat in the process. Such reversible photochemical process has been considered for developing solar thermal (MOST) systems. In this review, we introduce concept, criteria, and state-of-the-art of MOST systems, with an emphasis on three most promising systems: norbornadiene/quadricyclane, E/Z-azobenzene, dihydroazulene/vinylheptafulvene. After discussing fundamental working principles, focus design strategies improving energy storage performance, remaining challenges, potential areas. Finally, summarize current incorporation into functional devices conclude perspective challenges future directions.