Fluorine-Functionalized Pore-Space-Partitioned Metal-Organic Frameworks for One-Step Methane Purification

The efficient removal of ethane (C₂H₆) and propane (C₃H₈) from natural gas is vital for purification. A synergistic pore engineering integrating pore space partition and fluorine functionalization in metal-organic frameworks (MOFs), which may effectively promote the C-H···π and C-H···F interactions for effective methane separation. This strategy was validated using two fluorine-functionalized pore-space-partitioned MOFs (SNNU-707/-708) constructed by introducing varying numbers of -CF₃ groups on the pore surface. Single-component adsorption isotherms show high adsorption of SNNU-707/-708 for C₂H₆ and C₃H₈ were 94.9/63.6 cm³ g^-1 and 96.4/68.9 cm³ g^-1, significantly exceeding that of CH₄ (18.9/13.4 cm³ g^-1). Ideal adsorbed solution theory (IAST) indicated high selectivity values of 85.2/116.6 for C₃H₈/CH₄ (50/50) and 16.7/17.0 for C₂H₆/CH₄ (50/50). Notably, the actual breakthrough interval times of SNNU-707 for C₃H₈/CH₄ (5/95) and C₂H₆/CH₄ (10/90) can reach 502 and 78 min·g^-1 and yield high-purity CH₄ (>99.5%) at 5.89 mmol g^-1 from ternary mixtures. Grand Canonical Monte Carlo (GCMC) simulations attribute this performance to synergistic weak interactions (C-H···π, C-H···F, C-H···O/N) between MOF and alkane. Specially, thanks to the fluorine-functionalized pore environments, both MOFs maintain structural integrity and separation performance under harsh conditions up to 98% relative humidity, which is crucial for practical wet natural gas separation.