Size-Matching Ligand Insertion in MOF-74 for Enhanced CO₂ Capture under Humid Conditions

Among various class of materials, metal organic frameworks (MOFs) are one of the most promising candidates for CO₂ capture from flue gases. In particular, M-MOF-74, where M represents different metals, are equipped with open metal sites that can lead to very high CO₂ uptake at postcombustion flue gas conditions. However, these structures are known to have poor CO₂ capture performance under humid conditions as water molecules bind strongly to the unsaturated metal sites, outcompeting the CO₂. In this computational study, a pore space partition strategy is employed through a symmetry-matching regulated ligand insertion within the Mg-MOF-74 and Zn-MOF-74 structures, which mitigates the deterioration effect of water. In the case of Zn-MOF-74, higher selectivity as well as larger CO₂ uptake in binary mixture conditions is obtained, thereby demonstrating that reduction in the pore size of MOFs can serve as viable strategy to capture CO₂ under humid postcombustion conditions.