Construction of a Hydrophobic Metal–Organic Framework with Dense Oxygen Sites for Efficient CH4/N2 Separation under Humid Conditions

Abstract

Adsorption-based separation processes are of great significance for coalbed methane purification. However, most adsorbents are hydrophilic and cannot treat moist coal-mine methane. Herein, we report a hydrophobic metal–organic framework (MOF), Co-TBSC-ATC, with dense oxygen sites, constructed by a dual-ligand strategy. At 298 K and 1 bar, it exhibits a CH4 uptake of 13.2 cm3 g–1 and an ideal adsorbed solution theory (IAST) selectivity of 9.07, outperforming most hydrophobic adsorbents. Theoretical calculations revealed that the rational distribution of oxygen sites in its methyl-abundant pore channels facilitates C–H···O interactions with CH4, realizing a synergistic effect of hydrophobic resistance combined with selective adsorption. Dynamic breakthrough experiments demonstrated stable and efficient CH4/N2 separation under both dry and humid conditions, with outstanding recyclability. This work provides a feasible design strategy for hydrophobic MOFs that may be applied in the upgrading of low-grade coalbed methane.