Six Three-Dimensional Metal−Organic Frameworks with (3,4)-, (4,5)-, and (3,4,5)-Connected Nets Based on Mixed Ligands: Synthesis, Structures, and Adsorption Properties

Six new 3D metal−organic frameworks (MOFs) Cd2(3,4-PDC)2(μ2-hmt)(H2O)2·(DMF)2(H2O)2 (JUC-65), Zn4(3,4-PDC)4(μ2-hmt)(H2O)6·(DMA)4(H2O)5 (JUC-66), Cd2(3,4-PDC)2(bipy)2(H2O)2·(DMA)3(H2O)4 (JUC-67), Cd2(3,4-PDC)2(bipy)(DMF)(H2O)·(H2O)2 (JUC-68), Mn2(3,4-PDC)2(μ2-hmt)(H2O)2 (JUC-69), and Zn8(3,4-PDC)8(bipy)3(DMA)2·(DMA)8(H2O)8 (JUC-70) (3,4-H2PDC = pyridine-3,4-dicarboxylic acid, hmt = hexamethylenetramine, bipy = 4,4′-bipyridine, DMF = N,N′-dimethylformamide, DMA = N,N′-dimethylacetamide, and JUC = Jilin University China) have been synthesized via heterocoordination of unsymmetrical 3,4-H2PDC and transition metal ions (Cd2+, Zn2+, or Mn2+) to construct corrugated layers pillared by hmt or bipy ligands, which form various sizes and shapes of channels. Remarkably, from the topological point of view, JUC-65−68 exhibit three undocumented types of (3,4)-connected networks, JUC-69 exhibits a rare (4,5)-connected network, and JUC-70 possesses an unprecedented (3,4,5)-connected network. In addition, methanol adsorption isotherms of the activated JUC-65 and JUC-67 reveal type I behavior with approximately 87.7 mg/g and 124.8 mg/g at room temperature, respectively.