Mixed-Solvothermal Syntheses and Structures of Six New Zinc Phosphonocarboxylates with Zeolite-type and Pillar-Layered Frameworks

Six zinc phosphonocarboxylate hybrid materials, namely, Zn₂(pbc)₂·2Hdma·DMF·H₂O (1), Zn₂(pbc)₂·H₂teta·H₂O (2), Zn(pbc)·H₃O (3), Zn₄(pbc)₃·HTEA (4), Zn₃(pbc)₂(en)₂ (5), and Zn₃(pbc)₂(H₂O) (6) (H₃pbc = 4-phosphono-benzoic acid, DMF = N,N-dimethylformamide, dma = dimethylamine, teta = triethylene tetramine, TEA = triethylamine, en = ethylenediamine) have been synthesized using organic amines as structure-directing agents under mixed-solvothermal condition. These new compounds have been characterized by X-ray single-crystal diffraction together with infrared (IR) spectroscopy, thermogravimetric (TG) analysis, and powder X-ray diffraction (XRD). In structures 1 and 2, the double crankshaft chains constructed by the corner-sharing of ZnO₄ and CPO₃ tetrahedra are cross-linked by the organic moieties of the ligands into three-dimensional (3-D) structures with GIS (gismondine) and GIS-related zeolite topologies. In structure 3, the connectivity between ZnO₄ and CPO₃ results in inorganic (4.6.12) sheets, which are pillared by the benzoic acid group −C₆H₅−COO− into a 3-D open framework structure with zeolitic SOD (sodalite) topology. Structures 4−6 are pillar-layered structures where the Zn−O−P layers show different configuration due to the directing effect from different organic amines and solvents employed during the synthesis. The results show that the amines and organic solvents acting as structure-directing agents along with control of reaction condition are effective in achieving varieties of zinc phosphonocarboxylate structures.