Enhanced CO₂CH₄ separation using hydroxyl functionalized Mg-MOF-74

The separation of carbon dioxide (CO₂) from methane (CH₄) is crucial for biogas upgrading and natural gas purification. In this study, Mg-MOF-74 was functionalized with 2,5-dihydroxy-1,4-benzenedicarboxylic acid (dobdc), introducing hydroxyl groups that enhance CO₂ adsorption through hydrogen bonding and quadrupole interactions. The resulting Mg-MOF-74-dobdc exhibited a remarkable CO₂ uptake of 9.12 mmol/g at 25 °C and 1 bar, surpassing unmodified Mg-MOF-74 and other leading adsorbents such as MIL-53(Al) and ZIF-8. This functionalization also significantly improved CO₂/CH₄ selectivity, exceeding 50 under low-pressure conditions. The synergistic effects of ligand functionalization enhanced adsorption capacity, exceptional selectivity, and operational robustness position Mg-MOF-74-dobdc as a promising benchmark for sustainable CO₂ capture in challenging gas separation processes.