Foldable, Stretchable, Superelastic, and Tunable Wettability Aramid Nanofiber Aerogels for Efficient Thermal Insulation and Oil–Water Separation

Aerogels hold great potential in thermal insulation, catalytic supports, adsorption, and separation, due to their low density, high porosity, and low thermal conductivity. However, their inherent mechanical fragility and limited control functionality pose substantial challenges that hinder their practical use. In this study, a strategy is developed for the fabrication of cross-linked aramid nanofiber aerogels (cANFAs) by combining internanofiber surface cross-linking with ice-templating techniques. This approach enables the production of cANFAs with an ultralow density of 6.3 mg/cm3 while exhibiting robust mechanical properties, including exceptional mechanical resilience, withstanding 90% compression in air and 80% compression underwater for 100 cycles, and high stretchability with a tensile strain of 34%. The cANFAs demonstrate remarkable thermal insulation properties, with low thermal conductivities of 0.03816 W/(m·K) at room temperature and 0.03518 W/(m·K) at −40 °C. Additionally, the cANFAs exhibit tunable wettability, being hydrophilic and oleophilic in air while becoming superhydrophobic underwater, which enables efficient gravity-driven oil–water separation performance. This study presents a promising route to create robust and functional aramid nanofiber aerogels for practical applications across various fields.