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.