Investigation of the composition space diagram of the ZnF2–3,5-diamino-1,2,4-triazole–HF–H2O chemical system and structural characterization of a new fluorinated guanazolate MOF [Zn3F2]·(Am2TAZ)4

The ZnF2–3,5-diamino-1,2,4-triazole–HF–H2O system has been explored by hydrothermal syntheses over a large domain of concentrations using micro-wave heating. In the composition space diagram, the crystallization areas of two fluorinated guanazolate MOFs, [Zn3F2]·(Am2TAZ)4 (I) and the previously described [ZnF]·(Am2TAZ) (II), have been defined (with Am2TAZ = 3,5-diamino-1,2,4-triazolate). Compound (I) (tetragonal, P 4/n n c (#126), a = 11.7055(6) Å, c = 7.3291(4) Å) was characterized by single-crystal X-ray diffraction, thermogravimetric measurement and 1H and 19F solid-state nuclear magnetic resonance (NMR) spectroscopy. Its crystal structure, showing a tfj topology, contains a unusual zinc double coordination. It can be described as infinite chains running along the crystallographic a- and b-directions in which clusters of Zn2N4 tetrahedra and ZnN4F2 octahedra alternate. The analysis of the ZnF2–HAm2TAZ–HF–H2O composition space diagram gives possible hints on a relationship between the HF concentration in solution and the zinc coordination environment in the final guanazolate fluorinated MOF obtained.