Optimizing the pore environment in biological metal–organic frameworks through the incorporation of hydrogen bond acceptors for inverse ethane/ethylene separation

The development of efficient adsorbents for the selective separation of ethane (C₂H₆) and ethylene (C₂H₄) is essential for the cost-effective production of high-purity ethylene. Here, we employ a pore engineering strategy to optimize the pore environment of biological metal-organic frameworks (MOFs) by incorporating hydrogen bond receptors to enhance the inverse separation efficiency of C₂H₆ and C₂H₄. Compared to the isomorphic Cu-AD-SA, the methyl-functionalized Cu-AD-MSA and Cu-AD-DMSA not only provide suitable pore confinement but also offer additional binding sites, thus creating an optimal environment for strong interactions with C₂H₆ (AD = adenine, SA = succinic acid, MSA = 2-methylsuccinic acid, and DMSA = 2,2-dimethylsuccinic acid). Adsorption results show that Cu-AD-DMSA exhibits remarkable C₂H₆/C₂H₄ selectivity (up to 2.4) as well as outstanding C₂H₆ adsorption capacity (3.63 mmol g^-1), surpassing most reported C₂H₆-selective MOFs. Theoretical calculations combined with in situ infrared spectroscopy reveal that the synergetic effect of suitable pore confinement, amino groups, and functional surfaces decorated with multiple methyl binding sites provides strong and multipoint interactions for C₂H₆. Breakthrough experiments demonstrate that Cu-AD-DMSA exhibits exceptional performance in separating binary C₂H₆/C₂H₄ gas mixtures. The high chemical and thermal stability, scalable synthesis, and economic viability of Cu-AD-DMSA illustrate its potential as a candidate for C₂H₆/C₂H₄ separation application.