In the petrochemical industry, ethane/ethylene (C2H6/C2H4) separation is one of the most important processes. Herein, we reported an iron-based metal organic framework MIL-142A for efficiently trapping C2H6 from C2H6/C2H4 mixture, exhibiting preferential adsorption of C2H6 over C2H4. After various characterization techniques to confirm the successful preparation of MIL-142A, the C2H6 and C2H4 adsorptive separation performance was systematically investigated. Results showed that MIL-142A had remarkably higher C2H6 adsorption capacities than that of C2H4 at 298, 288, and 278 K, such as C2H6 and C2H4 adsorption capacities of 3.8 and 2.9 mmol/g at 298 K and 100 kPa, respectively. In addition, the C2H6 and C2H4 adsorption heats were relatively low and in the corresponding ranges 27.3-25.1 and 26.2-23.8 kJ/mol, which is a favorable property for the regeneration of MIL-142A with less energy penalty. Furthermore, it was inferred that the difference between the adsorption heat for C2H6 and C2H4 with the MIL-142A framework governed the selective adsorption of C2H6 over C2H4. The ideal adsorbed solution theory (LAST) selectivity of C2H6/C2H4 was high up to 5.8 in the initial low pressure and then decreased to 1.5 at 298 K and 100 kPa. Besides, breakthrough experiments also corroborated its efficient separation of C2H6/C2H4 mixture. Additionally, MIL-142A had excellent moisture stability, and its framework remained still intact after being exposed to humid conditions (80% RH) for 15 days. These comprehensive properties demonstrated that this unique material MIL-142A, as a high-performance C2H6-selective adsorbent, can be potentially used for highly adsorptive separation of the C2H6/C2H4 mixture.