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

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.