Two Structurally Similar Co 5 Cluster-Based Metal-Organic Frameworks Containing Open Metal Sites for Efficient C 2 H 2 /CO 2 Separation.

To reasonably design and synthesize metal-organic frameworks (MOFs) with high stability and excellent adsorption/separation performance, the pore configuration and functional sites are very important. Here, we report two structurally similar cluster-based MOFs using a pyridine-modified low-symmetry ligand [HL = 2,6-bis(2',5'-dicarboxyphenyl)pyridine], [(NHMe)][Co(L)(OCH)(μ-OH)·2DMF]·2DMF·2HO () and [Co(L)(μ-OH)(HO)]·2HO·4DMF (). The structures of and are built from Co clusters, which have one-dimensional open channels, but their microporous environments are different due to the different ways in which ligands bind to the metals. Both MOFs have extremely high chemical stabilities over a wide pH range (2-12). The two MOFs have similar adsorption capacities of CH (144.0 cm g for and 141.3 cm g for ), but has a higher CH/CO selectivity of 3.5 under ambient conditions. The difference in gas adsorption and separation between the two MOFs has been compared by a breakthrough experiment and theoretical calculation, and the influence of the microporous environment on the gas adsorption and separation performance of MOFs has been further studied.