AbstractOne-step adsorptive purification of ethylene (C₂H₄) from four-component gas mixtures comprising acetylene (C₂H₂), ethylene (C₂H₄), ethane (C₂H₆) and carbon dioxide (CO₂) is an unmet challenge in the area of commodity purification. Herein, we report that the ultramicroporous sorbent Zn-atz-oba (H₂oba = 4,4-dicarboxyl diphenyl ether; Hatz = 3-amino-1,2,4-triazole) enables selective adsorption of C₂H₂, C₂H₆ and CO₂ over C₂H₄ thanks to the binding sites that lie in its undulating pores. Molecular simulations provide insight into the binding sites in Zn-atz-oba that are responsible for coadsorption of C₂H₂, C₂H₆ and CO₂ over C₂H₄. Dynamic breakthrough experiments demonstrate that the selective binding exhibited by Zn-atz-oba can produce polymer-grade purity (>99.95%) C₂H₄ from binary (1:1 for C₂H₄/C₂H₆), ternary (1:1:1 for C₂H₂/C₂H₄/C₂H₆) and quaternary (1:1:1:1 for C₂H₂/C₂H₄/C₂H₆/CO₂) gas mixtures in a single step.