Nanocellulose Aerogels Inspired by Frozen Tofu

Cellulose-based aerogels are reported that were generated using cellulose nanofibril (CNF) gels in an ambient drying process. These nancellulose aerogels were inspired by the preparation of a traditional Chinese food, frozen tofu, which undergoes significant toughening after freezing and thawing. It is this toughening mechanism that allows for the formation of nanocellulose aerogels which ordinarily would collapse upon ambient drying. By freezing hydrated CNF gel dispersions, solvent exchanging, and drying at ambient pressure, monolithic nanocellulose aerogels with high porosity (>98%), low density (as low as 0.018 g cm–3), and high surface area (>30 m2 g–1) were readily generated. Moreover, since no special reactors are required, these structures can be easily created over large areas. For example, a hydrated CNF gel was frozen at −72 °C, and then, the frozen gel was immersed directly in a 2-propanol bath to allow solvent exchange. The resulting alcohol-infused gel was dried at ambient pressure to fabricate monolithic CNF aerogels, enabling the scalable fabrication of nanocellulose aerogels in an energy-efficient and cost-effective manner.