In the chemical industry, it is significantly important but still a great challenge to achieve an efficient and energy-saving method for separating the ethane (C2H6)/ethylene (C2H4) binary mixture at ambient conditions. Adsorptive separation, as a promising alternative, can achieve C2H6/C2H4 separation with suitable high-performance adsorbents. In this study, we systematically investigated Ni-4PyC, a nickel-based MOF, for its interesting C2H6-selective adsorption behavior. At 298 K, the C2H6 adsorption capacity of Ni-4PyC was 3.84 mmol/g, which was higher than C2H4 (3.55 mmol/g). The adsorptive selectivity toward the C2H6/C2H4 (1:15, v/v) mixture was calculated to be 1.7. The molecular simulation showed that both the pore effect and hydrogen bonding governed the C2H6-selective adsorption behavior. Moreover, cyclic breakthrough experiments further confirmed the dynamic separation performance and excellent recyclability, during which no obvious change was observed for the breakthrough time of the two components. Therefore, as a C2H6-selective adsorbent with excellent cycle performance, Ni-4PyC exhibited relatively high adsorption capacity and moderate selectivity, making it a competitive candidate for further application in separating the cracking gas of the C2H6/C2H4 mixture.