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

Increased energy consumption, driven by climate change and the rise of new industries, has spurred a demand for alternative cooling technologies to replace energy-intensive systems and mitigate environmental pollution. Radiative cooling, leveraging the optical properties of materials to cool without emitting pollutants or consuming energy, is considered a suitable solution. Among the various form of radiative cooling devices, paint stands out as a practical application for radiative cooling. Hence, a passive daytime radiative cooling (PDRC) paint is developed using a polyurethane binder and zeolitic imidazolate framework (ZIF)-8. ZIF-8 is synthesized in an environmentally friendly manner using deionized water as the solvent, resulting in paint with a reflectance of 94.9%, emissivity of 94%, and cooling power of 113 W m⁻². Temperature measurements reveal that the paint reduced ambient temperatures by an average of 5.7 °C, reaching up to 8.1 °C during the day. Additionally, with a self-assembly monolayer coating, the PDRC surface exhibited super-hydrophobicity and self-cleaning capabilities. Therefore, the proposed ZIF-8-based PDRC paint offers sub-room temperature cooling potential and is anticipated to reduce energy consumption for cooling, thereby alleviating environmental pollution in various applications, particularly in building exteriors.