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.