Two ultramicroporous metal-organic frameworks assembled from binuclear secondary building units for highly selective CO/N separation.

Two novel metal-organic frameworks [Ni(μ-Cl)(BTBA)·DMF]·Cl·3DMF (JLU-MOF56, BTBA = 3,5-bis(triazol-1-yl)benzoic acid) and [Co(μ-Cl)(BTBA)·DMF]·Cl·3DMF (JLU-MOF57) have been successfully synthesized under solvothermal conditions. Crystallographic analysis indicates that the two compounds with different metal ions are isoreticular and both are constructed from binuclear [M(μ-Cl)(COO)N] (M = Co, Ni) and a 3-connected hetero-N,O donor ligand. The overall framework possesses a (3,6)-connected dag topology. Furthermore, both of them feature ultramicroporous channels of 3.5 Å× 3.4 Å, which are suitable for adsorbing smaller carbon dioxide (CO) gas molecules but not larger nitrogen (N) gas molecules. Therefore, JLU-MOF56 and JLU-MOF57 exhibit good performance for CO/N separation, and are promising materials for gas adsorption and purification.