Core-shell metal organic frameworks (MOFs) have emerged as a promising platform for efficient separation and sensing, benefiting from the sieving effect of the shell and the large storage capacity of the core. However, conventional core-shell MOFs often encounter challenges with compromised pore integrity, which predominantly restricts their design to microporous cores. In this study, a straightforward strategy to construct functional shells on mesoporous MOFs is proposed. By leveraging dynamic imine chemistry, small-molecule amines are assembled into supramolecular polymers and anchored onto the surface of mesoporous MOFs through metal coordination. This approach preserves the mesoporous structure of the core while introducing hydrogen-bonding channels in the shell, facilitating the selective capture and storage of polar gases. The resulting core-shell MOF demonstrates exceptional CO₂/N₂ selectivity of up to 10,943 and a high CO₂ adsorption capacity, enabling the direct production of high-purity CO₂ (99.7 vol.%) from humid flue gas in a single breakthrough experiment. Furthermore, this strategy exhibits excellent stability and versatility across various mesoporous MOFs, underscoring its potential for practical industrial gas separation applications.