MIL-101-Cr/Fe/Fe-NH₂ for Efficient Separation of CH₄ and C₃H₈ from Simulated Natural Gas

Adsorptive separation based on porous solid adsorbents has emerged as an excellent effective alternative to energy-intensive conventional separation methods in a low energy cost and high working capacity manner. However, there are few stable mesoporous metal-organic frameworks (MOFs) for efficient purification of methane from other light hydrocarbons in natural gas. Herein, we report a series of stable mesoporous MOFs, MIL-101-Cr/Fe/Fe-NH₂, for efficient separation of CH₄ and C₃H₈ from a ternary mixture CH₄/C₂H₆/C₃H₈. Experimental results show that all three MOFs possess excellent thermal, acid/basic, and hydrothermal stability. Single-component adsorption suggested that they have high C₃H₈ adsorption capacity and commendable selectivity for C₃H₈ and C₂H₆ over CH₄. Transient breakthrough experiments further certified the ability of direct separation of CH₄ from simulated natural gas and indirect recovery of C₃H₈ from the packing column. Theoretical calculations illustrated that the van der Waals force proportional to the molecular weight is the key factor and that the structural integrity and defect can impact separation performances.