A V-shaped microporous metal-organic framework with multiple binding sites for highly efficient ethane/ethylene separation

Development of ethane-selective porous materials for highly efficient ethane/ethylene (C₂H₆/C₂H₄) separation can energy-efficiently produce high-purity C₂H₄ in one step. Microporous metal-organic frameworks (MOFs) show great promise as ethane-selective materials; however, achieving both high C₂H₆ capacity and high C₂H₆/C₂H₄ selectivity in most reported MOFs remains a significant challenge. Herein, we report, for the first time, the strategy of designing V-shaped pore structure with multiple binding sites in an Al-MOF (CAU-8-ODB) to target both high C₂H₆ uptake and selectivity for highly efficient C₂H₆/C₂H₄ separation. This V-shaped micropore configuration not only enables a large number of inert phenyl rings surrounding the cage to provide stronger interactions with C₂H₆ over C₂H₄, but also provides enough pore spaces to take up large amount of C₂H₆. Gas adsorption studies reveal that CAU-8-ODB exhibits a combination of both large C₂H₆ adsorption capacity (3.30 mmol·g⁻¹ at 0.5 bar) and high C₂H₆/C₂H₄ selectivity (2.2) at 296 K and 1 bar, outperforming or comparable to most of top-performing materials reported. Theoretical calculations indicate that the V-shaped cavities with suitable pore spaces can provide stronger multipoint interactions with C₂H₆ than C₂H₄, accounting for both high C₂H₆ uptake and selectivity. The actual separation capacity of CAU-8-ODB was further testified by the breakthrough experiments for 50/50 (v/v) C₂H₆/C₂H₄ mixtures, affording a remarkably high C₂H₄ productivity of 15.1 L·kg⁻¹ with high purity of 99.95% under ambient conditions.