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

Abstract 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.