Template-Assisted 3D-PVDF Nanonetworks for Passive Daytime Radiative Cooling.

Passive daytime radiative cooling (PDRC), which dissipates heat through infrared emission to outer space while reflecting solar radiation, represents a promising strategy for reducing energy consumption in cooling technologies. Here, a template-assisted strategy is introduced to fabricate nanostructured polyvinylidene fluoride (PVDF) radiative coolers via polymer infiltration into three-dimensional anodic aluminum oxide (3D-AAO) nanoporous templates. The optical properties and cooling performance of the 3D-PVDF nanostructures are investigated with and without the AAO template. To tune the crystalline phase composition and its influence on optical response, three post-infiltration cooling methods-natural, fast, and ultra-fast-are applied. A UV treatment further enhances solar reflectance through photo-oxidation-induced whitening. The optimized free-standing 3D-PVDF obtained via ultra-fast cooling exhibits an average solar reflectance of 82.4% (0.32-2.5 μm) and an infrared emissivity of 96.7% within the 8-13 μm atmospheric window. These properties correspond to a theoretical daytime cooling power density of 182.3 W m-2 under a solar irradiance of 1000 W m-2. Outdoor measurements demonstrate a daytime temperature reduction of 12.9°C under peak solar irradiance of 962 W m-2 relative to an empty reference box. This work establishes a scalable strategy for engineering three-dimensional polymer nanostructures for high-performance radiative cooling and energy-efficient building technologies.