Humidity-Resistant Methane Single-Molecule Traps for Efficient Separation of Coal-Bed Methane

The rational design of efficient adsorbents for methane capture from coal-bed methane (CBM) is crucial for both energy utilization and environmental protection. In this study, a novel "methane single-molecular trap" (MSMT) architecture is reported within a metal-organic framework (MOF) for CH₄ capture from CBM, in which each MSMT is designed as a unique space that can accommodate only a single CH₄ molecule, surrounded by open metal sites (OMSs) and adjacent hydrophobic alkyl groups. The obtained adsorbent, MSMT-NKMOF-1, exhibits efficient separation of CH₄/N₂, achieves a dynamic selectivity of 9.2 and a CH₄ productivity of 22.6 L kg^-1 at 298 K and 1 bar. Furthermore, this design shows impressive humidity resistance. Combined experimental and theoretical analyses reveal that the MSMT design not only eliminates the "desert" regions for traditional adsorbents-where strong functional sites are inaccessible-thereby enhancing the dynamic selectivity, but also prevents moisture interference. Additionally, MSMT-NKMOF-1 can be synthesized rapidly and environmentally friendly at room temperature, providing feasibility for industrial CBM purification. The work not only develops MSMT-NKMOF-1 as a promising adsorbent for CH₄/N₂ separation, but also provides a generalizable guidance for the development of novel functional porous materials for related applications.