Nanopore Engineering in Scalable Metal-Organic Frameworks for C2H4 Purification from Ternary Mixtures

The selective separation of ethylene (C2H4), carbon dioxide (CO2), and acetylene (C2H2) remains a critical challenge owing to their strikingly similar molecular sizes, polarities, and physical properties. Herein, we demonstrate that precise engineering of a sub-nanometric pore environment in metal-organic frameworks (MOFs) enables optimal separation of ternary C2H2/CO2/C2H4 mixtures. By modulating the functional groups on triazole ligands and introducing H2msa as a flexible bridging linker, we assembled two pcu-type MOFs: Zn-Atz-Msa (1) and Zn-Mtz-Msa (2) (H2msa = methylsuccinic acid, Hatz = 3-amino-1, 2, 4-triazole, Hmtz = 3-methyl-1,2,4-triazole). Compound 1 features ultra-microporous channels suited for C2H2/C2H4 separation, whereas compound 2 exhibits significantly enhanced potential for multicomponent separation, attributable to its well-defined pore architecture and negatively charged pillar ligands that establish strong C-H···N and C-H···O/N interactions with C2H2 molecules. These structural and chemical attributes endow 2 with preferential C2H2 adsorption over C2H4 and CO2 in both binary and ternary mixtures, positioning it among the few materials capable of one-step purification of polymer-grade C2H4 from a C2H2/CO2/C2H4 (0.5/0.5/9.0, v/v/v) mixture. Notably, 2 can be synthesized at large scale via a straightforward reflux method, underscoring its practical potential as a rare and highly effective porous adsorbent for industrial gas separation and purification.