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

Abstract

Via hydrothermal synthesis, the self-assembly of M(II) ions, H3BTC or H2NDC 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)): {Co3(L1)3(BTC)2(μ-H2O)3·2H2O}n (1), {Zn2(L2)(HBTC)2·2H2O}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 (63)2(64·82)2(62·84) 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 HBTC2− 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 (42·62·82)(42·68) topology. 4 and 5 show 4-connected MOFs with 65·10 and 65·8 CdSO4-type topology, respectively. Furthermore, their thermal properties are studied by thermogravimetric analysis.