Passive control of temperature fluctuations through a sunlight-induced spin transition in a molecule-based material

The increasing environmental protection demand has prompted the development of passive thermal regulation systems that reduce temperature fluctuations in buildings. Here, we demonstrate that the heat generated by the sun can trigger a spin transition in a spin-crossover (SCO) material, resulting in a color change. This leads to a cooling effect in respect to other similar materials, due to an increase in light reflection. In addition, when the material is cooled, a dampening of the temperature decrease is produced. Therefore, these materials could potentially be implemented for passive temperature control in buildings. Furthermore, SCO materials are remarkably stable upon cycling and highly versatile, which allows for the design of compounds with properties tailored for the desired climatic conditions and comfort temperature.