Connecting small ligands to generate large tubular metal-organic architectures

The new metal-organic framework materials, ZnF(Am2TAZ)·solvents and ZnF(TAZ)·solvents (Am2TAZ=3,5-diamino-1,2,4-triazole, TAZ=1,2,4-triazole), have been synthesized solvothermally and structurally characterized by either Rietveld refinement from powder XRD data or by single crystal X-ray diffraction. The three-dimensional structures of the compounds display open-ended, tubular channels, which are constituted of covalently bonded hexanuclear metallamacrocycles (Zn6F6(ligand)6). The tubular channels are subsequently covalently joined into a honeycomb-like hexagonal array to generate the three-dimensional porous framework. In the case of ZnF(Am2TAZ)·solvents, hydrophilic –NH2 groups point into the channels, effectively reducing their inner diameter relative to ZnF(TAZ)·solvents. The present compounds are isostructural to one another and to the previously reported ZnF(AmTAZ)·solvents (AmTAZ=3-amino-1,2,4-triazole), illustrative of the fact that the internal size and chemical properties of the framework may be altered by modification of the small, heterocyclic ligand. In addition to demonstrating the ability to modify the basic framework, ZnF(TAZ)·solvents and ZnF(Am2TAZ)·solvents are two of the most thermally stable coordination frameworks known to date.