A Microporous Metal-Organic Framework with Unique Aromatic Pore Surfaces for High Performance C2H6/C2H4 Separation

Developing adsorptive separation processes based on C2H6-selective sorbents to replace energy-intensive cryogenic distillation is a promising alternative for C2H4 purification from C2H4/C2H6 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 C2H6/C2H4 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 C2H6 over C2H4 while the suitable pore spaces enforce its high C2H6 uptake capacity, featuring Ni-MOF 2 as one of the best porous materials for this very important gas separation. It generates 12 L/kg of polymer-grade C2H4 product from equimolar C2H6/C2H4 mixtures at ambient conditions.