Molecular-Rotor-Enhanced Pore-Space Partition in Metal-Organic Frameworks for Boosting One-Step Ethylene Purification

One-step ethylene purification from the ternary acetylene/ethane/ethylene (C₂H₂/C₂H₆/C₂H₄) mixture is a pivotal yet unresolved challenge in industrial petrochemical processes. Herein, a molecular-rotor-enhanced pore-space partition (MR-enhanced PSP) strategy is proposed, which successfully achieves synergistic optimization of pore environments in metal-organic frameworks for boosting one-step ethylene separation. The insertion of pore partitioners through open metal sites in typical MIL-88 framework precisely tunes the local pore apertures, while aromatic molecular rotors step-by-step regulate the pore windows and progressively enriches the π-π and C-H⋯π interactions with gas molecules. Optimized SNNU-636 adsorbent achieves a C₂H₂/C₂H₄ selectivity of 4.17, outperforming its counterparts without molecular rotors (SNNU-630: 1.78, SNNU-631: 3.29, SNNU-632: 1.42) and additionally exhibiting preferential adsorption of C₂H₆ over C₂H₄. Fixed-bed breakthrough experiments confirm that SNNU-636 enables one-step production of ultrahigh-purity C₂H₄ (> 99.9999%) from the ternary mixture with a record-high yield of 7.8 mmol·g^-1, surpassing all benchmark adsorbents under similar conditions. Mechanistic studies further validate this MR-enhanced PSP strategy, revealing that C₂H₂ and C₂H₆ are stabilized via multiple π⋯π and C-H⋯π interactions, underpinning the state-of-the-art one-step C₂H₄ purification performance.