Tuning Pore Chemistry of Metal–Organic Frameworks Using Anionic Pillars for Humid-Tolerant CO ₂ Capture

Reducing global CO 2 emissions is a critical challenge, and metal–organic frameworks (MOFs) have emerged as promising physisorbents for capturing trace amounts of CO 2 from wet flue gas and humid ambient air. The tunability of the MOF pore chemistry through functional moieties enables selective CO 2 capture over H 2 O. In this study, 18 hypothetical MOFs (hMOFs) were rationally designed by integrating chemical moieties previously explored for trace CO 2 capture. Anionic pillars (SiF 6 2– and SO 4 2– ), known to induce strong interactions with electrophilic CO 2, were incorporated into template MOFs (CALF20, CALF20-met-w, and CALF20-met-e) that have demonstrated efficacy in post-combustion CO 2 capture. These anionic pillars create nucleophilic pore environments that enhance the selectivity of CO 2 under humid conditions. Among the candidates, CALF20-SiF 6 -met-w, composed of Zn metal, methyl-triazolate, and SiF 6 2– anionic pillars, theoretically maintained CO 2 uptake efficiency above 92.4% across the entire relative humidity range, outperforming its template MOF and benchmark materials. To evaluate its practical applicability, we integrated this material into a temperature–vacuum swing adsorption (TVSA) process simulation. Parametric analysis revealed that it offers a more favorable trade-off between productivity and energy consumption than the template MOF, primarily attributable to its higher working capacity and lower H 2 O uptake under varying humidity conditions. This study demonstrates the potential of anion pillar engineering in MOFs to achieve efficient CO 2 capture under humid conditions.