Robust, thermal insulated cellulose porous films for durable and efficient radiative cooling

Cellulose-based radiative cooler has attracted significant attention due to its inherent infrared emissivity, customizable structure and eco-friendliness, but is restrained by low solar reflectance and environmental durability. This work addresses these challenges by integrating hexagonal boron nitride (BN) into cellulose matrix to form robust and thermal insulated cellulose porous films. BN serves as dual-functional filler which can strengthen the mechanical property, simultaneously induce the multi-scattering interfaces to enhance solar reflectance. Such designed cellulose composite films (RPCF_BN-40) possessed abundant and regular porous architecture, achieved the enhanced solar reflectance of 95.69% and infrared emissivity of 0.89. Benefiting from the micro-nano pore structures and high refractive BN, RPCF_BN-40 displayed exceptional thermal insulation with high thermal blocking ratio of 81.31%. The synergistically integrated radiative cooling and thermal insulation capabilities enabled RPCF_BN-40 with a maximum temperature drop of 19 °C under strong sunlight, and 5.3 °C on cloudy day, as well as 3.1 °C at night, demonstrating high-efficiency outdoor radiative cooling. Importantly, the structural integrity and the solar reflectance of RPCF_BN-40 were maintained after 360 h of UV aging. Thus, this work provides a feasible strategy to fabricate effective and durable cellulose radiative cooling materials in diverse weather conditions.