Thermal-Rectified Gradient Porous Nanocomposite Film Enabling Multiscenario Adaptive Radiative Cooling.

Micronanoporous structures hold high potential as radiative sky-cooling materials for zero-energy thermal regulation in enclosed spaces subjected to high temperatures and direct sunlight, owing to their combination of thermal insulation and sunlight scattering features. However, their constrained ability to reflect sunlight across the entire solar spectrum, coupled with the inefficient dissipation of excess internal heat, restricts their applicability in diverse cooling scenarios. Herein, we present a gradient cross-linked polymerization strategy for preparing a gradient porous nanocomposite film. This film features a dual-gradient distribution of nanoparticle content and pore size, achieving a solar reflectance of 96.2% and demonstrating thermal rectification properties with a thermal rectification factor of 30%. Functioning effectively as a thermally rectified radiative cooling panel, this gradient film delivers energy-efficient and adaptive cooling for multiple enclosed environments, regardless of whether indoor temperatures exceed or fall below ambient outdoor temperatures. This gradient film achieves an extra cooling effect of 2.4 and 2.2 °C for unheated and self-heated enclosed environments, respectively, compared to the cooling effect using conventional porous nanocomposite films. The gradient structural design for porous structural radiative cooling materials demonstrates multiscenario adaptive radiative cooling applications.