Porous Polyimide Films with Comprehensive Resistance to Extreme Environment for Passive Daytime Radiative Cooling and Energy Saving

Passive daytime radiative cooling (PDRC) materials have drawn worldwide attention in the past few years, since they can cool a surface without any energy consumption, significantly reducing global energy consumption. Compared with inorganic PDRC materials, polymeric PDRC materials present more advantages, including strong designability and machinability. However, their flammability and poor antiaging properties (resistance to ultraviolet light, acid, and heat) seriously restrict their sustainable applications. Herein, based on molecular design and microstructure control, a scalable preparation of a fluorine-containing porous polyimide (PPI) film with micro/nanopores is designed and prepared via a phase separation process. Owing to the presence of fluorine and an ideal micro/nanoporous structure, the resultant PPI film shows high sunlight reflectance (∼95.3%) and high mid-infrared (MIR) emissivity (∼94.2%), resulting in a temperature drop of ∼5.0 °C at daytime and an ultrahigh cooling power of ∼120.15 W m–2. Meanwhile, PPI films present flame retardancy and acid, UV, and thermal resistance, making them with ideal candidates for robust and durable daytime cooling. This work provides a powerful approach for developing polymeric durable PDRC materials with antiaging and flame-retardant applications.