Performance Degradation of Amine-Infused Fiber Sorbents for Direct Air Capture: Mechanisms and Solutions

Sorbent stability poses significant impacts on long-term performance of direct air capture (DAC) of CO₂ and levelized cost of capture (LCOC). We report the DAC performance degradation of amine-infused fiber sorbents based on poly-(ethylenimine) (PEI), mesoporous SiO₂, and cellulose acetate (CA) over CO₂ cyclic sorption cycles in a nonoxidative environment. Infrared and nuclear magnetic resonance spectra indicate that the aminolysis reactions between CA ester moieties and PEI amine sites lead to the formation of acetamides and hence lower CO₂ affinities of the sorbents. This stability issue can be remedied by hydrolysis treatment of the CA fiber sorbents before PEI impregnation or replacing CA with poly-(ether sulfone). This study underscores the importance of selecting proper support or additive materials of DAC contactors that are compatible with active species of CO₂ capture.