Push-Pull Bis-Norbornadienes for Solar Thermal Energy Storage

Area of Science:

• Materials Science
• Photochemistry
• Renewable Energy

Background:

• Molecular solar thermal energy storage (MOST) utilizes photoswitchable molecules like norbornadiene/quadricyclane (NBD/QC).
• Traditional NBD derivatives often exhibit limited overlap with the solar spectrum, hindering efficient energy absorption.
• Red-shifting absorption typically reduces the gravimetric energy density of NBD systems.

Purpose of the Study:

• To design and synthesize novel NBD dimers with enhanced solar spectrum absorption.
• To investigate the impact of dimeric structure on absorption properties and energy storage capacity.
• To evaluate the performance of new NBD dimers for high-performance MOST applications.

Main Methods:

• Synthesis of five new NBD dimer compounds.
• Spectroscopic analysis to determine absorption spectra and onsets.
• Thermal stability measurements to assess the half-life of the metastable isomer.
• Calculation of gravimetric energy density.

Main Results:

• The synthesized NBD dimers exhibit significantly red-shifted absorption spectra.
• One dimer shows the most red-shifted absorption onset (539 nm) and maximum (404 nm) reported for NBD systems.
• High energy densities of 379 kJ/kg were achieved.
• Long thermal half-lives of up to 23 hours at 25°C were maintained for the metastable isomer.

Conclusions:

• Dimeric NBD systems effectively mitigate the trade-off between red-shifted absorption and energy density.
• The developed NBD dimers demonstrate promising characteristics for efficient and practical MOST applications.
• These findings represent a significant advancement in the field of molecular solar thermal energy storage.