Multifunctional Superelastic Cellulose Nanofibrils Aerogel by Dual Ice‐Templating Assembly

Abstract A superelastic aerogel with fast shape recovery performance from large compressive strain is highly desired for numerous applications such as thermal insulation in clothing, high‐sensitive sensors, and oil contaminant removal. Fabrication of superelastic cellulose nanofibrils (CNF) aerogels is challenging as the CNF can assemble into non‐elastic sheet‐like cell walls. Here, a dual ice‐templating assembly (DITA) strategy is proposed that can control the assembly of CNF into sub‐micrometer fibers by extremely low temperature freezing (–196 °C), which can further assemble into an elastic aerogel with interconnected sub‐micron fibers by freezer freezing (−20 °C) and freeze drying. The CNF aerogel from the DITA process demonstrates isotropic superelastic behavior that can recover from over 80% compressive strain along both longitudinal and cross‐sectional directions, even in an extremely cold liquid nitrogen environment. The elastic CNF aerogel can be easily modified by chemical vapor deposition of organosilane, demonstrating superhydrophobicity (164° water contact angle), high liquid absorption (489 g g −1 of chloroform absorption capacity), self‐cleaning, thermal insulating (0.023 W (mK) −1 ), and infrared shielding properties. This new DITA strategy provides a facile design of superelastic aerogels from bio‐based nanomaterials, and the derived high performance multifunctional elastic aerogel is expected to be useful for a wide‐range of applications.