Large scalable, anti-ultraviolet, strong cellulose film with well-defined dual-pores for longtime daytime radiative cooling

Passive daytime radiative cooling technology, which reflects sunlight and emits thermal radiation simultaneously, shows great potential in releasing global warming and energy consumption. Particularly, cellulosic cooling materials, with the advantages of high infrared emissivity, eco-friendly, and easy processing, have gained great attention. However, the poor solar reflectance and the poor durability related to UV and mechanical properties still limited its broad applications. In this work, we developed a novel cellulose composite film (CCF) with a well-defined, hierarchical micro/nanostructure via a rational solvent-induced phase separation technology for efficient and longtime daytime radiative cooling. TiO2@PT synthesized via facile ball milling process was used to serve as a dual functional modifier, which can improve the optical, mechanical properties, and anti-UV function of the cellulose-based daytime radiative cooler. Benefiting from the hierarchical dual pores, formed tough interface, and assembled anti-UV functional network, the as-prepared CCF displayed ultrahigh solar reflectance of 97.6 % and enhanced Young's modulus and tensile strength increase by 13 and 4.4 times, respectively. Most importantly, the solar reflectance of CCF is maintained constant after continuous UV tests for 720 h. The work provides a general strategy to simultaneously enhance both the mechanical stability and the UV durability of polymer-based PDRC materials toward large-scale applications.