Biomimetic Liquid-Solid Interfaces for Selective and Moisture-Tolerant CO2 Chemisorption.

Porous liquids (PLs) combine accessible microporosity with liquid-like flow, enabling continuous operation beyond the macroscopic mass-transfer limits of packed solid adsorbents. Yet, enhancing the chemical selectivity of PLs while maintaining their fluidity and interfacial stability remains a fundamental challenge. Here, we report a biomimetic Type III PL that enables enzyme-like Zn-OH chemisorption in a fluidic environment by integrating Zn2+-coordinated covalent organic framework (COF) scaffolds with a hydroxyl-functionalized ionic liquid (IL). Hydroxyl groups on the IL cations undergo inward coordination to activate Zn2+ nodes within the triazine-based COF, generating structurally defined Zn-OH motifs that reside in a biomimetic liquid-solid interface, where an IL-induced polarity gradient selectively admits CO2 but excludes H2O. This counterintuitive interfacial segregation preserves the microporosity of the COF and protects the reactive Zn-OH centers, enabling high chemisorptive uptake (106 cm3 g-1) and exceptional CO2/N2 selectivity (1273) under ambient conditions. In situ IR spectroscopy directly captures the reversible Zn-OH/Zn-OCO2H cycle, and atomistic simulations reveal how IL-driven coordination and polarity gradients stabilize Zn-OH motifs while guiding CO2 penetration. These findings establish a general molecular-design principle for constructing chemically specific, moisture-tolerant active sites in fluidic porous media, opening a new regime of selective chemisorption in liquid-phase materials.