Mixed Metal–Organic Framework with Multiple Binding Sites for Efficient C 2 H 2 /CO 2 Separation

The separation of C 2 H 2 /CO 2 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 Å for C 2 H 2 /CO 2 separation. This MOF shows not only a remarkable volumetric C 2 H 2 uptake of 133 cm 3  cm −3 , but also an excellent C 2 H 2 /CO 2 selectivity of 24 under ambient conditions, resulting in the second highest C 2 H 2 ‐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 C 2 H 2 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 C 2 H 2 /CO 2 separation.