Developing adsorptive separation processes based on C2H6‐selective sorbents to replace energy‐intensive cryogenic distillation is a promising alternative for C2H4 purification from C2H4/C2H6 mixtures, which however remains challenging. During our studies on two isostructural metal–organic frameworks (Ni‐MOF 1 and Ni‐MOF 2), we found that Ni‐MOF 2 exhibited significantly higher performance for C2H6/C2H4 separation than Ni‐MOF‐1, as clearly established by gas sorption isotherms and breakthrough experiments. Density‐Functional Theory (DFT) studies showed that the unblocked unique aromatic pore surfaces within Ni‐MOF 2 induce more and stronger C−H⋅⋅⋅π with C2H6 over C2H4 while the suitable pore spaces enforce its high C2H6 uptake capacity, featuring Ni‐MOF 2 as one of the best porous materials for this very important gas separation. It generates 12 L kg−1 of polymer‐grade C2H4 product from equimolar C2H6/C2H4 mixtures at ambient conditions. Benefiting from the unblocked unique aromatic pore surfaces, suitable pore spaces and pore volumes, Ni‐MOF 2 displays high separation performance for C2H6/C2H4 separation and produces polymer‐grade C2H4 with high productivity (12 L kg−1) by a single separation process.