Durable hierarchically porous polyurethane membrane for efficient passive daytime radiative cooling

Passive daytime radiative cooling (PDRC) is an advanced thermal management strategy that achieves cooling by minimizing solar absorption while efficiently radiating heat into cold outer space, offering a promising solution for global thermal regulation. Inspired by the micron-scale porous networks widely distributed in white fungus, we fabricated a hierarchically porous polyurethane (PU) membrane with high porosity and low density via a non-solvent-induced phase separation (NIPS) process combined with solvent evaporation, using a pore-forming agent and incorporating hydrophobic silica nanoparticles. The resulting membrane exhibits a solar reflectance of 95.7 % and an emissivity of 94.5 % within the atmospheric window, delivering outstanding radiative cooling performance with a maximum temperature reduction of 5.95 °C under outdoor testing. Moreover, when integrated with textiles, the membrane forms hierarchically porous fabrics that maintain considerable reflectance after friction, acid–alkali and UV-resistance tests, while hydrophobic modification further endows the material with enhanced self-cleaning capability. This durable porous PU membrane holds great potential for applications in personal thermal management, energy-efficient buildings, and electronic device cooling.