Co-Assembled MOF@SiO2 Nanostructures for Superhydrophobic and Electrically Insulating Radiative Cooling Coatings

Passive radiative cooling (PRC) technology, characterized by zero-energy cooling capability, has shown great promise for thermal management of high-voltage electrical equipment. However, such application scenarios impose stringent multifunctional requirements on PRC coatings, including superhydrophobicity to resist surface contamination, as well as high electrical insulation strength to prevent surface flashover. Here, we report a co-assembly strategy for constructing multifunctional PRC coatings through the in situ integration of a metal-organic framework (MOF) with a silica precursor. The appropriately tailored bandgap (Eg = 4.25 eV) of the MOF, slightly exceeding the upper photon-energy bound of the measured solar band (4.13 eV), enables suppressed solar absorption while affording a strong mid-infrared emissivity. Meanwhile, the high-Eg SiO2 shell effectively passivates intrinsic insulation defects and the high surface energy associated with MOFs, thereby enhancing both dielectric reliability and superhydrophobicity. Consequently, the optimized PRC coating delivered a temperature drop of 10.6 ± 0.5 °C during outdoor testing, together with robust superhydrophobicity (153.7°) and high wet flashover strength (15.6 kV/cm). This work advances PRC coatings beyond conventional thermal regulation by integrating radiative cooling, surface self-cleaning, and electrical insulation into a unified material platform, opening new opportunities for passive thermal management of high-voltage electrical equipment.