UV‐Resistant Hierarchical Porous Coatings with Tailored Thermal‐Optical Properties for Extreme Diurnal Temperature Variations

Effective thermal management is essential for maintaining habitable conditions and system reliability in environments with extreme diurnal temperature variations. However, conventional thermoregulatory materials fail to deliver bidirectional thermal regulation under such conditions. Radiative coolers often cause excessive nocturnal overcooling due to continuous heat loss. Conversely, pure thermal insulators cannot actively dissipate accumulated heat during the day. Prolonged UV exposure further accelerates material degradation, compromising long‐term performance stability. Overcoming these compounding environmental challenges necessitates a unified design strategy. Here, we present UV‐resistant hierarchical structured thermoregulatory (HiST) coatings that synergistically integrate high‐performance radiative cooling and superior thermal insulation within a scalable architecture. The coatings show outstanding thermal‐optical properties: 97.58% solar reflectance with robust UV rejection, 97.34% infrared emissivity, and 35 mW m −1 K −1 thermal conductivity. Field tests in extreme environments reveal ∼19.8°C temperature reduction relative to an uncoated control and ∼4.1°C peak nighttime interior temperature elevation above the ambient, buffering interiors against thermal shocks. This work establishes a robust materials platform for effective thermal management in applications ranging from energy‐efficient buildings to spacecraft and habitats for extreme terrestrial and space environments.