Designing Molecular Solar Thermal Systems Based on the Paternò–Büchi Reaction Coupled to Enzymatic Energy Release

Molecular solar thermal systems are attracting considerable attention as an alternative to conventional batteries for storing chemical energy, making it possible to use sunlight as external storage input, while releasing the stored energy as heat. Despite such interest, acceptable results are obtained only by modifying the norbornadiene-quadricyclane system, still leaving key issues unsolved. Here, a full storage-release molecular solar thermal systems cycle based on the Paternò-Büchi reaction is designed, potentially offering a class of compounds with a significantly higher storage density than norbornadiene-quadricyclane. Based on the experimental evidence concerning the viability of their synthesis and photoreactivity, those compounds are repurposed by computationally elucidating the substitution pattern effects on low-energy isomer's light absorption, followed by high-energy isomer's photoproduction, including singlet and triplet states involved by the Paternò-Büchi type of reactivity. The thermal conversion back to the initial isomer to release the stored energy is also studied, including a sustainable option by taking advantage of enzymatic activity.