Design of highly efficient, renewable chlorine-modified metal-organic frameworks and investigation of CH4/N2 separation performance

The efficient separation and enrichment of methane (CH 4 ) from low-concentration coalbed methane (CBM) are of great significance for enhancing CBM utilization efficiency and promoting the development of low-carbon clean energy. To address this practical need, this study synthesized a tailored chlorinated metal-organic framework (MOF), PCP-IPA-Cl, and systematically evaluated its CH 4 /N 2 separation performance through a combination of static adsorption measurements, density functional theory (DFT) calculations, dynamic breakthrough experiments, and multiple adsorption-desorption cycling tests. Endowed with its optimized pore structure and chlorinated channel environment, PCP-IPA-Cl exhibits excellent CH 4 /N 2 separation performance and regeneration stability: at 298 K and 1 bar, it achieves a high CH 4 adsorption capacity of 21.27 cm 3 /g with a low N 2 uptake of only 5.29 cm 3 /g, and compared with its unchlorinated analog PCP-IPA, the CH 4 /N 2 selectivity is markedly improved from 5.4 to 9.0. DFT calculations reveal that the introduction of–Cl groups creates additional preferential adsorption sites for CH 4 molecules, strengthening host-guest interactions and thus enhancing separation efficiency. Furthermore, breakthrough experiments confirm its excellent dynamic separation ability, and cyclic tests demonstrate that PCP-IPA-Cl can be fully regenerated via helium purging within just 5 min. These findings collectively demonstrate that PCP-IPA-Cl is a promising and regenerable adsorbent for the efficient enrichment and utilization of low-concentration CBM.