Syntheses, Structures, and Structural Transformations of Mixed Na(I) and Zn(II) Metal–Organic Frameworks with 1,3,5-Benzenetricarboxylate Ligands

Three new compounds, [ZnNa(BTC)(H2O)2]·H2O (1), [Zn3Na2(BTC)2(HCOO)2(H2O)8] (2), and [Zn3Na(BTC)2(HCOO)(H2O)3]·2H2O (3) (H3BTC = 1,3,5-benzenetricarboxylate acid), were synthesized under hydrothermal conditions and were characterized by the single crystal and powder X-ray diffraction, IR spectra, elemental analyses, ICP measurements, and coupled TG-MS analyses. 1, 2, and 3 crystallize in the space groups P1̅, C2/c, and P1, respectively. They are three-dimensional (3D) frameworks, consisting of zigzag chains ((Na2Zn2O14)n for 1, (Na2Zn3O18)n for 2, or (NaZn3O14)n for 3) and bridging BTC ligands. Powder X-ray diffraction studies reveal that 1 and 2 exhibit reversible dehydration–rehydration behaviors with a crystal-to-crystal transformation observed for 2.