A Microporous Metal-Organic Framework with Unique Aromatic Pore Surfaces for High Performance C₂ H₆ /C₂ H₄ Separation

Developing adsorptive separation processes based on C₂ H₆ -selective sorbents to replace energy-intensive cryogenic distillation is a promising alternative for C₂ H₄ purification from C₂ H₄ /C₂ H₆ mixtures, which however remains challenging. During our studies on two isostructural metal-organic frameworks (Ni-MOF 1 and Ni-MOF 2), we found that Ni-MOF 2 exhibited significantly higher performance for C₂ H₆ /C₂ H₄ separation than Ni-MOF-1, as clearly established by gas sorption isotherms and breakthrough experiments. Density-Functional Theory (DFT) studies showed that the unblocked unique aromatic pore surfaces within Ni-MOF 2 induce more and stronger C-H⋅⋅⋅π with C₂ H₆ over C₂ H₄ while the suitable pore spaces enforce its high C₂ H₆ uptake capacity, featuring Ni-MOF 2 as one of the best porous materials for this very important gas separation. It generates 12 L kg^-1 of polymer-grade C₂ H₄ product from equimolar C₂ H₆ /C₂ H₄ mixtures at ambient conditions.