Amine-based polymers, such as polyethyleneimine (PEI), have shown potential for direct air capture (DAC) of CO2 when incorporated into porous scaffolds. Adsorption conditions, including CO2 concentration, temperature, and amine loading, significantly influence the overall CO2 capture capacity and amine efficiency by affecting both diffusional resistance and reaction kinetics. In three-dimensional impregnated sorbents, internal diffusion can complicate the evaluation of intrinsic reaction kinetics at the air/amine interface. To isolate and study these kinetics, we used quartz crystal microbalance with dissipation (QCM-D) to investigate the CO2 adsorption on amine-based polymer thin films. Polyvinyl amine, liner PEI, and branched PEI were evaluated. The CO2 capture capacity and efficiency were measured as a function of film thickness, CO2 concentration, and temperature. The adsorption data were fitted to Avrami kinetic models. This study provides insight into the structure–property relationships of CO2 adsorption in amine-based polymers and offers guidance for the rational design of next-generation DAC sorbents.
