Engineered molecule stashes enough sunlight to boil water months later

Solar panels are a foolproof way to harness sunlight for electricity on the cheap. But capturing and storing the sun’s heat energy is not easy.Researchers have now created an organic molecule that stores a record amount of photon energy in its chemical bonds and releases it as heat on demand (Science 2026, DOI: 10.1126/science.aec6). The molecule, derived from the aromatic compound pyrimidone, is water-soluble and can store energy for up to 3 years. When triggered by an acid catalyst, the material releases enough heat to bring water to a boil in 0.5 s. It can then be recharged with light and reused.“We can recycle the molecule as fuel instead of burning it irreversibly,” as is done, for example, with natural gas and other fuels, says Grace Han, a chemistry professor at the University of California, Santa Barbara. “Once you charge it with light, you don’t have to worry about discharging like a battery.” The fuel solution can be mixed into water stored in a tank and triggered to release heat for buildings, she says.The engineered pyrimidone stores a record 1.65 MJ of energy per kilogram, more than a lithium-ion battery and much than any compound reported so far in the budding area of molecular solar thermal (MOST) energy storage. A MOST compound absorbs sunlight and undergoes transformation to a high-energy isomer. That form of the molecule stores energy in its strained bonds until a trigger makes it relax and revert to its original structure, emitting heat in the process.Han, Ken