pH-Controlled Assembly of 3D and 2D Zinc-based Metal-Organic Frameworks with Tetrazole Ligands

We report the synthesis and structural diversity of Zn(II) MOF with in situ formation of tetrazole ligand 3-ptz [3-ptz = 5-(3-pyridyl)tetrazolate], as a function pH. By varying the initial reaction pH, we obtain high-quality crystals of the non-centrosymmetric 3D MOF Zn(3-ptz)2, mixed phases involving the zinc-aqua complex [Zn(H2O)4(3-ptz)2]·4H2O, and 2D MOF crystals Zn(OH)(3-ptz) with a tunable micro-rod morphology, keeping reaction time, temperature and metal-ligand molar ratio constants. Structures are characterized by X-ray diffraction, scanning electron microscopy, FTIR and UV-Vis spectroscopy. We discuss the observed structural diversity in terms of the relative abundance of hydroxo-zinc species in solution for different values of pH.