Highly absorbent cellulose nanofibrils aerogels prepared by supercritical drying

•CNFs and TO-CNFs cryogels and aerogels obtained by freeze-drying and supercritical drying.•Different pore size distributions influenced by the process and the type of nanocellulose.•Capillary water uptake of porous structure investigated on skin mimicking layers.•TO-CNFs aerogels (482 m²/g) have water uptake capacities of ca. 120 times their own weight. In this paper, strictly speaking aerogels of cellulose nanofibrils (CNFs) and TEMPO-oxidized CNFs (TO-CNFs) were obtained from an optimized supercritical drying processes and cryogels were prepared after freeze-drying. The cryogels and aerogels were characterized and the influence of the preparation process on the resulting properties was studied. Significant differences were observed in the micro- and nanoscale organization of the porous structures. In addition, the specific surface areas measured varied from 25 to 160 m² g−1 for CNF materials, depending on the preparation process. Very high specific surface areas up to 482 m² g−1 among the highest reported for pure cellulose nanofibrils porous materials were achieved for TO-CNF aerogels. Finally, in order to evaluate their aptitudes for wound dressings applications, the capillary water uptake capacities were assessed on skin mimicking layers. From this study, it was revealed that TO-CNF aerogels can absorb almost 120 times their own weight of water.