Engineering the Microporous Environment of Flexible Metal–Organic Frameworks with Bifunctionality for Promoting the Separation of Ethylene from a Ternary Mixture

The separation of ethylene (C₂H₄) from mixtures with carbon dioxide (CO₂) and acetylene (C₂H₂) is of great industrial importance but remains a critical challenge. Here, we report that a rationally designed flexible metal-organic framework (FMOF), featuring a specifically engineered microporous environment with bifunctionality, can promote the efficient one-step separation of C₂H₄ from a ternary mixture. Adsorption isotherms and dynamic breakthrough tests provide experimental evidence confirming the selective adsorption of CO₂ and C₂H₂ over C₂H₄ on such a FMOF, as well as its ability to separate C₂H₄ from a CO₂/C₂H₂/C₂H₄ ternary mixture. Theoretical calculations and simulations provide critical insights into the flexible adsorption process and the separation mechanism of the FMOF. The bifunctionality incorporated in FMOF provides exceptionally strong binding of CO₂ and C₂H₂ but inhibition of C₂H₄, which, in turn, enables high adsorption selectivity for CO₂/C₂H₄ and C₂H₂/C₂H₄. This FMOF has high potential for industrial applications in the separation of C₂H₄ from gas mixtures.