Optimizing HostGuest Interaction Sites in Metal‐Organic Frameworks for Benchmark One‐Step Ethylene Purification

ABSTRACT Purifying ethylene from ternary acetylene/ethylene/ethane (C ₂ H ₂ /C ₂ H ₄ /C ₂ H ₆ ) mixture in one‐step requires preferential adsorption for C ₂ H ₂ and C ₂ H ₆ , which is challenging due to the intermediate physicochemical property of C ₂ H ₄ . To address this problem, a synergistic host‐guest interaction strategy is proposed for metal‐organic frameworks (MOFs) by taking open metal site (OMS) to preferentially bind with electron‐rich C ₂ H ₂ through π‐coordination interaction, while saturated hydrocarbon C ₂ H ₆ primarily adsorbed via C‐H∙∙∙π interactions with aromatic rings (AR). The feasibility of this strategy was demonstrated by three conformational isomeric 8‐connected [Fe ₃ ( µ ₃ ‐O)(COO) ₆ ] trigonal prismatic trinuclear cluster‐based robust MOFs (denoted as SNNU‐705‐α/β/γ regulated by amino groups). Combining one unoccupied OMS site and occupying AR groups in SNNU‐705‐α/β/γ boosts the C ₂ H ₂ and C ₂ H ₆ affinity and binds C ₂ H ₄ the weakest. Aided by amino Lewis basic sites (LBSs) furtherly, SNNU‐705‐γ exhibits the highest C ₂ H ₆ uptake at 298 K and 1 atm (6.13 mmol g ⁻¹ ) among all reported MOFs for one‐step C ₂ H ₄ purification. Breakthrough experiments indicate that all SNNU‐705‐α/β/γ can separate C ₂ H ₄ from C ₂ H ₂ /C ₂ H ₄ /C ₂ H ₆ mixture in one‐step with exceptional productivity (purity > 99.9999%) of 7.07, 6.75, and 5.46 mmol g ⁻¹ , far surpassing all adsorbents reported so far. In situ FT–IR spectra and DFT calculation validates this strategy and indicate their potential in industry applications.