Highly efficient subambient all-day passive radiative cooling textiles with optically responsive MgO embedded in porous cellulose acetate polymer

Passive radiative cooling (PRC) is an electricity-free and spontaneous cooling technology to alleviate the global scorching weather that increasingly threatens human health. Herein, combined with the calculation to reveal the full-spectrum optical constants of MgO and predict its remarkable optical responsiveness for PRC applications. Guided by this calculation, a highly efficient subambient all-day PRC textile is designed by embedding the MgO NPs into porous cellulose acetate (CA) polymer and then dip-coated onto the polyester (polyethylene terephthalate, PET) matrix (PET-CA-MgO). The resulting cooling textile shows both of high solar reflectivity (94.6%) and high infrared emissivity (96.8%), which is found to be originated from the superposition of the optical properties of phonon polariton resonance of MgO (the Fröhlich mode) and Mie scattering of porous CA polymer. More importantly, its theoretical net PRC powers are calculated up to 117.8 and 156.1 W m⁻² during the daytime and nighttime, respectively, which is on par with the state-of-the-art. Under direct sunlight, the PET-CA-MgO based PRC textile achieves a subambient temperature reduction of 8 °C, and enables simulated skin to avoid overheating by ∼11 °C as compared to bare skin heater and pristine PET textile. This design strategy for the spectral selective feature of textiles presents an effective approach to further fabricate high-performance PRC garments for practical purposes.