Solution-processable, robust and sustainable cooler via nano-structured engineering

Passive daytime radiative cooling (PDRC) materials simultaneously featuring aesthetic and safety distinctions demonstrate versatile applications beyond cooling buildings, while the integrated advantages of high strength, morphological reconfigurability, and sustainability remain challenging for the conventional PDRC materials. Herein, we designed a robust, custom-shaped and eco-friendly cooler via a scalable solution-processable strategy, involving the nano-scale assembly of nano cellulose (NC) and inorganic nanoparticle (e.g., ZrO2, SiO2, BaSO4, and hydroxyapatite). The robust cooler shows an interesting brick-and-mortar structure, where the NC con-structs interwoven framework (as brick structure) and the inorganic nanoparticle uniformly locates in the skeleton (as mortar structure), collectively contributing to high mechanical strength (>80 MPa) and flexibility. In addition, the structural and chemical distinctions enable our cooler to show a high solar reflectance (>96 %) and mid-infrared emissivity (>0.9), demonstrating a sub-ambient average temperature drop of 8.8 degrees C in long-term outdoor environments. The high-performance cooler with robustness, scalability and environmental friendli-ness, serves as a competitive participant toward the advanced PDRC materials in our low-carbon society.

Automated summary

We designed a robust and eco-friendly cooler by assembling nano cellulose and inorganic nanoparticles using a scalable solution-processable strategy. The cooler features a brick-and-mortar structure, with the nano cellulose forming the interwoven framework and the inorganic nanoparticles uniformly distributed in the skeleton, contributing to high mechanical strength and flexibility. It also exhibits high solar reflectance and mid-infrared emissivity, resulting in a significant temperature drop in outdoor environments.