Comparison of characteristics of the cellulose nanocrystal aerogels aminosilane-functionalized through gas-phase reaction

The cellulose nanocrystal (CNC) aerogels through freeze-drying (FD) and supercritical CO 2 drying (SC) were functionalized using aminosilane via vapor-phase reaction, and then they were characterized with a few different techniques. It was shown that the distinct microstructures in both pristine CNC aerogels generated no difference in their amine loading, being about 7.2 mmol g −1 . The grafting reaction took place only on the CNC surfaces, and more amorphous phase from the aminosilane was formed in the CNC-FD aerogel than in the CNC-SC one during the modification. As a result, the modified CNC-FD (m-CNC-FD) aerogel exhibited a lower crystallinity and thermal stability than the modified CNC-SC (m-CNC-SC) one. The dual Langmuir isotherm model gave a good description of CO 2 adsorption on both modified CNC aerogels. The m-CNC-FD aerogel gave a greater chemical affinity to CO 2 than the m-CNC-SC one, but the latter exhibited a greater chemisorption capacity for CO 2 than the former. The two modified aerogel exhibited a different adsorption–desorption profiles for CO 2 . However, the total CO 2 uptakes for the m-CNC-FD and the m-CNC-SC aerogels were up to 2.5 mmol g −1 at 25 ℃ and 100 kPa, and the temperature for its complete removal was 108 ℃. Therefore, the similarity in the CO 2 adsorption performance illustrated that both the CNC aerogels were all good porous materials of aminosilane for CO 2 capture.