Various White MOFs-based Cryogels for Passive Daytime Radiative Cooling

Abstract

Passive radiative cooling technology is a pressing need in contemporary society, yet it remains in its nascent stages and necessitates further research endeavors. In this study, a series of metal-organic frameworks (MOFs)-based cryogels have been synthesized through the freeze-drying method. The presence of abundant pore structures and chemical bonds (such as C-O, C-H, C-N, P=O, Ti-O, C-OH) imparts these MOFs-based cryogels with high solar reflectance values exceeding 90% and high mid-infrared emissivity levels surpassing 95%. These MOFs-based cryogels can reduce the temperature by at least 10 ℃ and up to 15.1 ℃ under direct sunlight. Notably, the structures and optical properties of these MOFs-based cryogels remain unchanged after being exposed to sunlight for 7 days and immersed in water for 30 days, indicating their good performance durability. Following accelerated ultraviolet aging and multiple freeze-thaw cycles, the cryogels' macroscopic appearances and microscopic morphologies remain intact, validating their exceptional weatherability. Furthermore, their recyclability and sustainable performance make them well-suited for applications as radiative cooling materials. The integration of MOFs and cryogels not only advances radiative cooling technology but also establishes a novel research platform for materials in this field.