Mixed Metal–Organic Framework with Multiple Binding Sites for Efficient C₂H₂/CO₂ Separation

The separation of C₂H₂/CO₂ is particularly challenging owing to their similarities in physical properties and molecular sizes. Reported here is a mixed metal-organic framework (M'MOF), [Fe(pyz)Ni(CN)₄] (FeNi-M'MOF, pyz=pyrazine), with multiple functional sites and compact one-dimensional channels of about 4.0 angstrom for C₂H₂/CO₂ separation. This MOF shows not only a remarkable volumetric C₂H₂ uptake of 133 cm³ cm^-3, but also an excellent C₂H₂/CO₂ selectivity of 24 under ambient conditions, resulting in the second highest C₂H₂-capture amount of 4.54 mol L^-1, thus outperforming most previous benchmark materials. The separation performance of this material is driven by π-π stacking and multiple intermolecular interactions between C₂H₂ molecules and the binding sites of FeNi-M'MOF. This material can be facilely synthesized at room temperature and is water stable, highlighting FeNi-M'MOF as a promising material for C₂H₂/CO₂ separation.