New Solar Fuel Boils Water in Half a Second

Can chemist bottle sunlight? In the continuing search for energy that does not rely on fossil

fuelssolar energy remains a key focus. An active area of research in the solar energy field is in molecular solar thermal (MOST) energy storage. A MOST system absorbs UV light and stores it for release on demand at a later time. A MOST molecule absorbs sunlight and transforms it into a high energy isomer that traps energy in its chemical bonds. Then a trigger is used to revert it to its original state, and this process releases heat.

A recent Science article reports an advance in renewable-energy chemistry. Researchers at UC

Santa Barbara and UCLA have engineered a pyrimidone-based MOST molecule that can store sunlight

for up to three years. What is remarkable about this molecule is that it is water-soluble and stores 1.65

MJ/kg of stored energy, the most of any MOST compound to date. This is more than a lithium-ion

battery. The new compound, when triggered by an acid catalyst, released enough energy to boilapproximately a half milliliter of water in half a second.

This MOST system was inspired by the structure of DNA whose bases absorb UV light and form

pyrimidones. The researchers engineered a new molecule by adding methyl groups to the hexagonal ring of one of these pyrimidones. The UV light is absorbed by the molecule and creates a new bond that forms two square units from the hexagon. When acid is used to break the bond, the isomer returns to the original shape and releases heat. The isomer that is created is called a Dewar-photoisomer, and its bonds are highly strained which allows it to store a large amount of energy. The system can be recharged with light and can be reused over and over again.

The scientific community is excited about this advance because it appears scalable and is easy to

synthesize. The water solubility opens up new possibilities for its uses. One drawback is that it takes a

long time to charge, so extensions of the research should focus on charging it more rapidly.

Articles used: 

https://cen.acs.org/energy/solar-power/Engineered-molecule-stashes-enoughsunlight/104/web/2026/02 

https://www.science.org/doi/10.1126/science.aec6413