Cryopolymerization‐Enabled Superelastic and Thermomechanically Robust Silica‐Sheathing Nanofibrous Aerogels for Solar‐Thermal Regulatory Cooling

Abstract Aerogels show significant potential for subambient thermal regulation in energy‐efficient buildings and personal thermal management under intense sunlight and hot conditions owing to their unique combination of thermal superinsulation and solar scattering characteristics. However, traditional aerogels encounter challenges in balancing mechanical flexibility with high‐temperature stability. Herein, a straightforward and scalable cryopolymerization strategy is presented for preparing a superelastic and thermomechanically robust silica‐sheathing nanofibrous aerogel. During cryopolymerization, cryogenic conditions create an ice crystal‐constrained microenvironment with interwoven cellulose nanofibers and concentrated silicate monomers. This confined microenvironment promotes the in situ condensation polymerization of high‐concentration silicates into porous silica nanoclusters predominantly on the nanofiber surfaces, resulting in an aerogel composed of bacterial nanocellulose cores encapsulated by silica sheaths. These aerogels demonstrate remarkable mechanical elasticity and thermal superinsulation, maintaining high stability even after prolonged exposure to calcination at 800 °C and direct exposure to 1200 °C butane flames. By precisely modulating sunlight and mid‐infrared light, these aerogels achieve a high solar reflectivity of 96.2% and an atmospheric window emissivity of 97.5% in extremely hot environments. Consequently, these parasitic‐heat‐insulating aerogels serve as energy‐efficient solar‐thermal regulatory cooling materials, achieving a notable temperature reduction of 11.4 °C for subambient environments under intense sunlight exposure and hot conditions.