A high-strength radiative cooling biocomposite via hierarchical crystalline nanostructuring.

Radiative cooling materials, which passively dissipate heat by reflecting sunlight and emitting infrared radiation through the atmospheric window, hold transformative potential for energy-efficient and sustainable thermal management. In particular, biomass-derived coolers have gained attention for their natural optical properties and environmental compatibility. However, such materials often depend on energy-intensive or complex processing to achieve the necessary photonic structures, while their limited mechanical strength and durability restrict practical outdoor application. Here, we report a high-performance, fully recyclable radiative cooling biocomposite fabricated directly from natural wood through an energy-efficient top-down approach that combines multi-stage crystalline restructuring with nanostructural assembly. This design synergistically combines enhanced cellulose crystallinity, capillary-driven self-densification, and hydrogen-bonded nanofiller networks to achieve exceptional mechanical properties (416.7 MPa tensile strength) and unprecedented cooling power (106 W/m2), surpassing most conventional cooling materials. During the daytime, field tests validate 8.8 °C sub-ambient temperature reduction under 879 W/m2 solar irradiance. The cooling biocomposite, produced at scale via particle-solution shock process, exhibits high recyclability and foldability, completing an environmentally conscious life cycle. The energy‑efficient manufacturing process enables meter‑scale production, offering a promising pathway toward carbon‑neutral thermal management in sustainable buildings and agricultural applications.