Hydrothermal Synthesis of Metal−Organic Frameworks Based on Aromatic Polycarboxylate and Flexible Bis(imidazole) Ligands

Via hydrothermal synthesis, the self-assembly of M(II) ions, H 3 BTC or H 2 NDC with three structure-related flexible bis(imidazole) ligands, L1, L2, and L3, generated six metal−organic polymers (M = Co, Ni, Zn; BTC = 1,3,5-benzenetricarboxylate, NDC = 1,2-benzenebicarboxylate, L1 = 1,4-bis(imidazol-1-ylmethyl)benzene, L2 = 1,1′-(1,4-butanediyl)bis(imidazole), L3 = 1,1′-(1,4-hexanediyl)bis (imidazole)): {Co 3 (L1) 3 (BTC) 2 (μ-H 2 O) 3 ·2H 2 O} n ( 1 ), {Zn 2 (L2)(HBTC) 2 ·2H 2 O} n ( 2 ), {Co(L3)(HBTC)} n ( 3 ), {Co(L1) (NDC)} n ( 4 ), {Ni(L2)(NDC)} n ( 5 ), and {Co(L3) (NDC)} n ( 6 ). The structure of 1 is the rare 4-connected self-penetrating metal−organic framework (MOF) with the (6 3 ) 2 (6 4 ·8 2 ) 2 (6 2 ·8 4 ) topology notation; polymers 2 and 6 are two-dimensional (2D) (3,4)-connected and 4-connected nets, respectively. If the O − H … O/2.631 Å hydrogen bonds between HBTC 2− dianions are not accounted for, then polymer 3 is a 2D (3,5)-connected net; contrarily, it is a pillar-layered three-dimensional supramolecular framework characterized by (4,5)-connected (4 2 ·6 2 ·8 2 )(4 2 ·6 8 ) topology. 4 and 5 show 4-connected MOFs with 6 5 ·10 and 6 5 ·8 CdSO 4 -type topology, respectively. Furthermore, their thermal properties are studied by thermogravimetric analysis.