Studies on the influence of drying processes on cellulose nanofiber (CNF) aerogel performance has always been a great challenge. In this study, CNF aerogels were prepared via two different drying techniques. The CNF solution was prepared via existing chemical methods, and the resultant aerogel was fabricated through supercritical CO2 drying and liquid nitrogen freeze-drying techniques. The microstructure, shrinkage, specific surface area, pore volume, density, compression strength, and isothermal desorption curves of CNF aerogel were characterized. The aerogel obtained from the liquid nitrogen freeze-drying method showed a relatively higher shrinkage, higher compression strength, lower specific surface area, higher pore volume, and higher density. The N2 adsorption capacity and pore diameter of the aerogel obtained via the liquid nitrogen freeze-drying method were lower than the aerogel that underwent supercritical CO2 drying. However, the structures of CNF aerogels obtained from these two drying methods were extremely similar.

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At present, cellulose nanocrystal (CNC) aerogels with high adsorption properties for CO 2 are mostly prepared by the liquid phase method which leads to the problem of modifier loss. In this work, a novel amino CNC aerogel was developed by chemical vapor deposition using 3-(2-aminoethylamino)-propylmethyldimethoxy silane (APS) as the modifier, which improved the utilization ratio of the modifier while ensuring the CO 2 adsorption performance. Herein, the as-prepared APS− CNC aerogel was characterized with elemental and functional groups and thermal, morphological, and structural characteristics by various measurements (X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, and Brunauer−Emmet− Teller equation). It exhibited a porous network structure with low specific surface area (29.14 m 2 /g) and excellent thermal stability. Furthermore, the CO 2 adsorption capacity of the CNC aerogel grafted with APS reached 1.5034 mmol/g (25 °C, 1 bar, and pure dry CO 2 atmosphere). Meanwhile, the APS−CNC aerogel showed excellent CO 2 adsorption/desorption recyclability after 10 cycles. The experimental results showed that the CNC aerogel modified by chemical vapor deposition had an important potential role as a biomass CO 2 solid adsorbent.

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