Construction of fluorescence active MOFs with symmetrical and conformationally rigid N-2-aryl-triazole ligands

1,4-Bis-triazole-substituted arene (NAT) was designed and synthesized for the construction of metal organic frameworks. Unlike the tri-phenyl analogs, which give a twisted conformation between three benzene rings due to the A-1,3 repulsion, the NAT-ligand gave the energetically favored co-planar conformation with the strong fluorescence emission. With this ligand, two new MOFs, NAT-MOF-Cd (2,3,4-c) and NAT-MOF-Cu (4-c), were successfully obtained with the structure confirmed by X-ray. With the six-coordinated Cd(ii) cluster, an interesting metal-ligand coordination and H-bonding hybridized porous polymeric structures were observed. In contrast, a typical Cu(ii) paddle wheel coordination was obtained with NAT and Cu, giving a new MOF structure with moderate stability in aqueous solution from pH 1-11 for 24 hours, which suggests a promising future for applications in fluorescence sensing and photocatalysis.