Various technologies have been developed to harness solar energy as a renewable resource to address the increasing global energy demand. In this context, Molecular Solar-Thermal (MOST) energy storage systems have emerged as promising candidates, particularly for overcoming the intermittency inherent in conventional solar technologies. MOST systems rely on molecular photoswitches capable of capturing, converting, storing, and releasing solar energy in a closed, emission-free, and on-demand fashion. Notably, the norbornadiene-quadricyclane (NBD-QC) couple is one of the most extensively studied. However, its practical application has primarily been confined to organic solvents. Although water-soluble NBD derivatives have been reported, they typically exhibit poor spectral overlap with solar radiation. Building upon these efforts, we synthesized a new NBD derivative incorporating a push–pull electronic system to enhance solar absorption and a hydroxamic acid moiety to ensure full-range aqueous solubility. Its energy storage capabilities were systematically evaluated in aqueous environments, revealing notable pH-dependence. Deprotonation improved both spectral properties and solubility; however, it also reduced the quantum yield and stability compared to the neutral NBD. We quantified energy storage density in solution using isothermal titration calorimetry (ITC), corroborating these findings with solid-state measurements conducted via differential scanning calorimetry (DSC). The results demonstrated a close agreement between solution and solid-state energy storage density, approaching the threshold of 0.3 MJ∙kg−1 for practical applications. Our findings underscore the feasibility of using push–pull functionalized NBD derivatives in aqueous solution under carefully controlled pH-conditions. Moreover, they encourage the exploration of green-solvent mixtures to further enhance MOST performance within environmentally friendly systems.
A new protic water-soluble norbornadiene with a push-pull system for energy storage in aqueous solution
Savastano, Matteo
2026-01-01
Abstract
Various technologies have been developed to harness solar energy as a renewable resource to address the increasing global energy demand. In this context, Molecular Solar-Thermal (MOST) energy storage systems have emerged as promising candidates, particularly for overcoming the intermittency inherent in conventional solar technologies. MOST systems rely on molecular photoswitches capable of capturing, converting, storing, and releasing solar energy in a closed, emission-free, and on-demand fashion. Notably, the norbornadiene-quadricyclane (NBD-QC) couple is one of the most extensively studied. However, its practical application has primarily been confined to organic solvents. Although water-soluble NBD derivatives have been reported, they typically exhibit poor spectral overlap with solar radiation. Building upon these efforts, we synthesized a new NBD derivative incorporating a push–pull electronic system to enhance solar absorption and a hydroxamic acid moiety to ensure full-range aqueous solubility. Its energy storage capabilities were systematically evaluated in aqueous environments, revealing notable pH-dependence. Deprotonation improved both spectral properties and solubility; however, it also reduced the quantum yield and stability compared to the neutral NBD. We quantified energy storage density in solution using isothermal titration calorimetry (ITC), corroborating these findings with solid-state measurements conducted via differential scanning calorimetry (DSC). The results demonstrated a close agreement between solution and solid-state energy storage density, approaching the threshold of 0.3 MJ∙kg−1 for practical applications. Our findings underscore the feasibility of using push–pull functionalized NBD derivatives in aqueous solution under carefully controlled pH-conditions. Moreover, they encourage the exploration of green-solvent mixtures to further enhance MOST performance within environmentally friendly systems.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
