Zeolitic Imidazolate Framework -8–Based Passive Daytime Radiative Cooling Paint for Energy-Efficient Cooling

Owing to increasing energy consumption, especially for cooling, as well as climate change and the emergence of new industries, there is a growing demand for new cooling technologies to replace the existing systems that consume a large amount of energy and contribute to environmental pollution. To overcome these problems, radiative cooling can be utilized, which uses the optical properties of materials to achieve cooling without emitting pollutants or consuming energy. Paint is the most practical form for the application of a radiative cooling material. Therefore, we fabricated a passive daytime radiative cooling (PDRC) paint using a polyurethane binder and zeolitic imidazolate framework (ZIF)-8 powder. The ZIF-8 powder was synthesized in an environmentally friendly manner using deionized water as the solvent, and the resulting paint had a reflectance of 94.9%, an emissivity of 94%, and a cooling power of 113 W/m2. Actual temperature measurement results showed that the paint cooled the surroundings by an average of 5.7 °C and up to 8.1 °C during the daytime. As a result, ZIF-8–based PDRC paint is capable of cooling below room temperature and is expected to reduce the energy used for cooling and alleviate environmental pollution in various fields, such as building exteriors<b>.</b>