A pillar-layered MOF bearing N/O sites for one-step purification of C2H4 from the mixtures with C2H6 or C3H6

Abstract

One-step adsorptive separation of high-purity ethylene (C₂H₄) from the mixtures with ethane (C₂H₆) or propylene (C₃H₆) is of crucial importance in the petrochemical industry. Nevertheless, the development of porous materials that possess both high adsorption capacities and selectivities of C₂H₆ and C₃H₆ over C₂H₄ is still a formidable challenge. Herein, we present a microporous pillar-layered metal–organic framework (MOF) that exhibits excellent uptake capacities of C₂H₆ (4.73 mmol g⁻¹) and C₃H₆ (8.05 mmol g⁻¹) at 298 K and 1 bar, leading to high adsorption selectivities for equimolar mixtures of C₂H₆/C₂H₄ (1.6) and C₃H₆/C₂H₄ (16.4), respectively. Breakthrough column experiments demonstrate that the MOF could achieve one-step acquisition of polymer-grade C₂H₄ (> 99.9 %) during C₂H₆/C₂H₄ and C₃H₆/C₂H₄ separations. Noteworthily, for a C₃H₆/C₂H₄ mixture (2/5, v/v), high-purity C₂H₄ (> 99.9 %) and C₃H₆ (> 99.5 %) can be directly harvested or recovered upon desorption, with high productivities of 86.23 and 31.05 L kg⁻¹, respectively, surpassing many well-developed adsorbents for C₃H₆/C₂H₄ separation. Theoretical calculations reveal that the nonpolar pore surface bearing accessible N and O atoms affords more hydrogen bonding interactions with C₂H₆ and C₃H₆ than C₂H₄, accounting for the adsorption affinity in the order of C₃H₆ > C₂H₆ > C₂H₄. This work may offer valuable insights into the design and construction of high-performance MOFs for one-step C₂H₄ purification.