Unveiling the states of polyamines in confined spaces and their impacts on the <scp> CO ₂ </scp> adsorption/diffusion process

Abstract The existing state of macromolecular amines in the confined space and their impacts on the kinetic and thermodynamic performance is the frontier issue in the research field of sorbent‐based CO 2 capture. This work studied the amine state in the confined space and the corresponding effects on CO 2 diffusion. The results demonstrated that amine molecules with different molecular weights exhibited two distinct loading states, namely the “spreading” and “stacking” states. By establishing a diffusion model based on the non‐equilibrium thermodynamics theory (NeTD), it was demonstrated that only when the CO 2 intramolecular diffusion and intrapore diffusion in polyethyleneimine were matched, the overall diffusion resistance would be the lowest. This study provides a pathway to understanding the amine molecules in the molded sorbents, which facilitate the advancement of sorbent‐based CO 2 capture in the scale‐up process and guide the design of molded amine sorbents with low mass transfer resistance and high working capacity.