High capacity and robust moisture-swing CO2 adsorption for direct air capture by functionalized cellulose aerogels

• High-capacity functionalized cellulose aerogels developed for moisture-swing CO 2 capture. • MSQCA achieved CO 2 sorption capacities of 2.37 mmol/g with shape recovery properties. • Robust structural stability and durability during 30 wet-dry cycles documented. • CER-MSQCA composites reached a CO 2 capacity of 3.71 mmol/g with rapid kinetics. • CER-MSQCA features hierarchical pores with tunable shapes for diverse DAC processes. Direct air capture (DAC) of CO 2 based on the moisture-swing mechanism (MSDAC) presents a more energy efficient alternative compared with other regeneration mechanisms in DAC technologies. However, its industrial implementation has been hindered by the inadequate CO 2 adsorption capacity, structural and mechanical instability of current MSDAC adsorbents under cyclic dry-wet conditions. This study addresses these challenges by developing advanced MSDAC materials with enhanced performance and durability as well as optimized morphology that enables up-scaling and easy maintenance for potential industry applications. Three types of functionalized cellulose aerogels (CA) were synthesized and evaluated. Among them, maleic acid-sodium hypophosphite-crosslinked quaternized cellulose aerogel (MSQCA) demonstrated the highest CO 2 desorption capacity (2.37 mmol/g), surpassing literature values for biomass-based adsorbents. MSQCA also exhibited excellent mechanical integrity and structural stability, maintaining performance over 30 dry-wet cycles in the tests. To further improve CO 2 capacity and scalability, MSQCA was combined with a high-capacity cation exchange resin (ACD-100) to form a CER-MSQCA composite. This composite features hierarchical porous structures and retains excellent processability, enabling the fabrication of versatile shapes for diverse industrial applications. The CER-MSQCA composite achieved a CO 2 desorption capacity of 3.71 mmol/g, alongside rapid desorption kinetics and superior durability under moisture swing conditions. These findings demonstrate the potential of hierarchical functionalized cellulose aerogels and their composites as high-performance, durable adsorbents for moisture-swing CO 2 capture, paving the way for their industrial implementation in direct air capture technologies.