From Global Flexibility to Local Flexibility: Enable A–B Stacked Metal–Organic Framework for One‐Step Ethylene Purification from Complex Gas Mixtures

Flexible metal–organic framework (MOF) adsorbents can achieve exceptional separation performances under appropriate stimuli, especially for complex gas mixtures. However, their intrinsic global flexibility often leads to unsatisfactory separation selectivity, which hampers the practical applications. Herein, we propose a “rotor‐locker” strategy to convert an A–B stacked Cd‐MOF‐GF (GF = global flexibility) into Cd‐MOF‐LF (LF = local flexibility) for efficient one‐step C2H4 separation from multiple complex gas mixtures. The grafted methyl groups serve as lockers to suppress global flexibility while preserving local stimulus‐responsive behavior. As a result, Cd‐MOF‐LF exhibits a 10‐fold increase in C2H2 uptake (1.95 mmol g−1) compared to Cd‐MOF‐GF (0.19 mmol g−1) at 0.1 bar and 298 K, yielding a record selectivity of 9.2 for C2H2/C2H4 (50/50) among similar adsorbents. Moreover, the selective capture of C2H6 and CO2 impurities is also significantly enhanced. Dynamic breakthrough experiments demonstrate that the Cd‐MOF‐LF column enables direct separation of polymer‐grade C2H4 (>99.9%) with a high productivity of 0.79 mmol g−1 from a quaternary C2H2/C2H6/CO2/C2H4 (1v/33v/33v/33v) gas mixture. Density functional theory calculations reveal a lower deformation energy (−3.99 kJ mol−1) and specific adsorption sites for Cd‐MOF‐LF.