Programmed Pore Engineering in an Isoreticular Triazole-MOF Series for One-Step Ethylene Separation

Ethylene (C₂H₄) purification from CO₂/C₂H₂/C₂H₄ ternary mixtures is industrially crucial yet remains highly challenging. Current metal-organic frameworks (MOFs) lack the ideal CO₂ > C₂H₂ > C₂H₄ adsorption sequence necessary for stepwise removal of impurities. Herein, we address this gap through precise pore environment tuning within an isoreticular series of zinc-triazole MOFs. By modulating the number and position of ─NH₂/─CH₃ groups on the ligand, we precisely control pore chemistry from one-dimensional (1D) channels to two-dimensional (2D) interconnected channels, which successfully achieves the targeted adsorption order. The unilateral amino groups in the optimized MOF, ZSTU-30, create unique supramolecular interlocking sites that strongly bind CO₂ while mitigating interactions with C₂H₄ and C₂H₂. Consequently, ZSTU-30 enables the direct production of polymer-grade C₂H₄ (> 99.9%) from a ternary gas mixture in a single step, with an exceptional C₂H₄ productivity of 3.18 mmol g^-1. The CO₂-host interaction mechanism is elucidated by in situ single-crystal X-ray diffraction and theoretical calculations, which reveal multiple supramolecular interactions at the adsorption sites. Combining excellent water and pH stability, ZSTU-30 stands out as a robust and promising physisorbent for one-step C₂H₄ purification.