Hydration Topology Manipulates CO₂ Transport in Water-Saturated Micropores of Functionalized Covalent Organic...

The confinement effect of nanochannels (<2 nm) dictates the gas-liquid distribution at solid-liquid interfaces, yet the effect of interfacial chemistry on their kinetic behaviors lacks insightful understanding. Particularly, the interfacial CO₂ transport mechanism is critical for CO₂ capture in hydrated environments. Herein, we employ nonequilibrium molecular dynamics simulations combined with density functional theory calculations to elucidate CO₂ transport mechanisms in fully hydrated one-dimensional micropores of covalent organic frameworks (COFs). Our results demonstrate that pore-wall chemistry regulates transport not directly through adsorption strength alone, but by reshaping the topology and dynamic organization of confined hydration networks. Without functionalization, the pristine COF channels form an ordered hydration structure that anchors CO₂ on adsorption sites and imposes substantial across-layer transport resistance. Functionalization of pore walls disrupts this hydration organization, accelerating CO₂ transport via distinct microscopic regimes and promoting spatial coexistence of CO₂ and water. Notably, fluorine functionalization establishes a mobility-dominated regime that minimizes friction, inverting the preference from H₂O-favored to CO₂-favored transport and achieving a nearly 3-fold increase in axial selectivity. This work reveals that CO₂ transport is controlled by hydration-mediated transport energetics. These findings offer molecular-level perspectives for design of microporous materials by highlighting importance of balancing interfacial affinity and transport resistance within confined hydration environments.