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

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.