Optimizing the cask effect in multicomponent natural gas purification to provide high methane productivity

The efficient separation of CH₄ from natural gas containing C₂H₆ and C₃H₈ impurities is an important topic. Previous work on the separation of CH₄/C₂H₆/C₃H₈ mixtures often focuses on the C₃H₈/CH₄ selectivity, inadvertently sidelining the critical importance of C₂H₆/CH₄ selectivity. This oversight results in reduced CH₄ productivity and compromised separation efficiency, a phenomenon often termed as the “cask effect.” Herein, we fine-tune the interrelationship between thermodynamics and kinetics, targeting enhanced CH₄ production. A synergistic thermodynamic–kinetic C₃H₈/CH₄ and C₂H₆/CH₄ selectivity is achieved using dynamic breakthrough experiments, underpinned by the stable metal–organic framework TIFSIX-Cu-TPA. The CH₄ productivity in TIFSIX-Cu-TPA is up to 5 mmol g⁻¹, surpassing most of the popular materials. Detailed density functional theory and molecular dynamics computational insights reveal a counteractive thermodynamic–kinetic relationship, proving pivotal for the simultaneous breakthrough of C₂H₆ and C₃H₈ under optimal conditions. Moreover, precise adsorption sites of C₂H₆ and C₃H₈ are clearly determined through in situ single-crystal structures.