Multistate Azobenzene-Norbornadiene Photoswitches for Molecular Solar Thermal Energy Storage

Area of Science:

• Materials Science
• Photochemistry
• Renewable Energy

Background:

• Molecular solar thermal (MOST) systems require high quantum yield and long-lived isomers for efficient energy storage.
• Combining photochromic molecules into multimodal photoswitches is a promising strategy for MOST applications.
• Achieving both high stability and efficient switching in MOST materials remains a significant challenge.

Purpose of the Study:

• To develop novel bi- and trimodal azobenzene-norbornadiene (AZO-NBD) photoswitches with synergistic properties.
• To investigate the independent switchability and stability of individual components within the hybrid photoswitch.
• To assess the potential of integrated AZO units for enhancing the half-life of NBD systems for MOST applications.

Main Methods:

• Synthesized AZO-NBD photoswitches by coupling AZO and NBD units via ester linkages.
• Conducted photochemical studies to analyze the switching behavior and isomer dynamics of the hybrid systems.
• Determined quantum yields and half-lives for both NBD and AZO components separately within the hybrid structure.
• Performed comparative analysis with reference systems to validate the extended half-life of NBD components.

Main Results:

• Demonstrated that both NBD and AZO components within the hybrid photoswitches are independently switchable.
• Achieved selective production of all isomer types in specific configurations.
• Extended the half-life of NBD components up to 122 days through integration with AZO units.
• Observed enhanced back-conversion rates facilitated by trifluoroacetic acid (TFA) catalysis.

Conclusions:

• The developed AZO-NBD photoswitches exhibit synergistic effects, enabling independent control over molecular components.
• Integration of AZO units significantly enhances the stability of NBD isomers, addressing a key challenge in MOST systems.
• These findings pave the way for designing more efficient and stable materials for molecular solar thermal energy storage.