Butterfly-inspired, nano-cement-engineered wood aerogel for superhydrophobic and flame-retardant passive daytime cooling

Bio-based radiative cooling materials offer a promising pathway toward sustainable and carbon-free thermal management. However, their practical application is often constrained by limited cooling efficiency, inherent hydrophilicity, and flammability. Inspired by the photonic architecture of Pieris rapae butterfly wings, a biomimetic wood cement aerogel featuring a "pane-nanobeads" structure was developed. This was achieved through in-situ anchoring of cement-based nanoparticles followed by fluorination modification. Benefiting from its unique bioinspired design, the resulting aerogel exhibited a high solar reflectance of 91.3% and an infrared emissivity of 99.1%, enabling a cooling temperature of 11.6 °C and a net cooling power of 84.8 W/m² under solar irradiance of 800 W/m². In hot regions of China, this performance translates to annual cooling energy savings of approximately 43.6 MJ/m². Furthermore, the material demonstrated exceptional superhydrophobicity, flame resistance, and remarkable environmental durability. Even after severe accelerated weathering involving extreme thermal cycling and intense UV irradiation, the aerogel maintained its structural integrity, superhydrophobicity, and a robust cooling drop of 9.4 °C. This work presents a scalable and effective strategy for designing high-performance, fire-safe radiative cooling materials, advancing the development of eco-friendly passive cooling technologies.