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

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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.