Cation Effects on Pre‐Reactive CO 2 Accessibility and Interfacial Transfer in Aqueous Glycinate Solutions via Molecular Dynamics

Alkali‐metal amino acid solutions are attractive liquid sorbents for carbon capture. Potassium glycinate shows more favorable CO 2 capture behavior than sodium and lithium analogues despite sharing the same reactive amine motif. However, the molecular origin of this countercation effect remains unresolved. Here, we use molecular dynamics simulations to examine how K + , Na + , and Li + regulate CO 2 accessibility and transport in aqueous glycinate solutions. We treat CO 2 uptake as a multistep process in which interfacial accessibility and transport precede chemical conversion, and we isolate this pre‐reactive stage. Li + forms a compact coordination environment with glycinate and water, restricting molecular mobility and reducing CO 2 access to glycinate‐centered regions. In contrast, K + maintains a more diffuse solvation environment, supporting higher diffusivities, larger interfacial CO 2 populations, and more frequent vapor‐to‐liquid transfer events. Collectively, these results identify interfacial gating, defined as cation‐dependent control of CO 2 population and exchange frequency at the vapor–liquid boundary, as the interfacial manifestation of a cation‐controlled CO 2 accessibility mechanism around glycinate.