Amino-functionalized nanocellulose aerogels for the superior adsorption of CO₂ and separation of CO₂/CH₄ mixture gas

Nanocellulose-based aerogels have been considered as one of the ideal candidates for CO₂ capture in practical applications owing to their lightweight and porous properties. Additionally, various adsorbents with amine groups have been widely used as effective CO₂ capture and storage strategies. Herein, amino-functionalized aerogels were prepared by sol-gel and freeze-drying methods using two typical nanocelluloses (cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs)) as substrates. In addition, the reaction parameters for grafting and amino functionalization were optimized. The CNC and CNF aerogels could be easily modified by the hydrothermal growth of the amino group, and they exhibited attractive properties in terms of CO₂ adsorption, recyclability, thermal stability, hydrophobicity, and CO₂/CH₄ mixture separation. The amino-functionalized CNF aerogel exhibited superior performance to the CNC aerogel, which was attributed to the increased cross-linking binding sites for hydrogen bonding in the CNF aerogel. The results of this study indicated that amino-functionalized nanocellulose aerogels can be considered a promising biodegradable, sustainable, and environmentally friendly material for CO₂ capture and removal of CO₂ from CH₄.