Synthesis And Luminescent Property Of Pyridine Polycarboxylate Metal-Organic Frameworks

Metal-Organic Frameworks (MOFs) is one kind of highly crystalline organic-inorganic hybrid materials connected by some kinds of chemical bonds between metal ions or metal-based points as connection centers and organic ligands as bridge linkers. MOFs not only have fascinating topological architectures, but also exhibit particular optical, electrical, magnetic, catalytic and absorption properties, especially the unique optical property make it has extensive and attractive potential applications, such as light emitting device, fluorescence detection, molecular (ions) recognition, biological fluorescent label, imaging and so on.This paper designed and synthesized three novel pyridine polycarboxylate organic ligands:4,4’-bipyridine-2,6-dicarboxylic acid (H2bda),5-(4-carboxyphe-nyl)-2,6-py-ridinedicarboxylic acid (H3cpda) and4-(3,5-dicarboxyphenyl)pyrid-ine-2,6-dicarboxylate (H4dpda). Using these ligands, Ln3+and Zn2+we synthesized four kinds of MOFs, Ln(bda)3-5H2O (Ln=Sm, Eu, Gd, Tb, Dy), Zn7O(cpda)3(OH)3,[Ln(H2cpda)(Hcpda)(H2O)]·(H2O)(Ln=Eu, Tb, Tbo.95Eu0.05) and [Ln(Hdpda)(H2O)4]·0.5(H2O)[Ln=Eu, Gd, Tb, Dy, Tb1-xEux(x=0.1-10%)], by solvethermal method. The structure and luminescent property were studied by single crystal X-ray diffraction analysis, PXRD, TGA, EA and photo-luminescent spectra.Study demonstrates that Ln(bda)3·5H2O (Ln=Sm, Eu, Gd, Tb, Dy) are OD isostructure, and its thermal stability is not very good. Under325nm excitation, Ln(bda)3·5H2O (Ln=Sm, Eu, Dy) exhibit strong characteristic emission of Sm3+, Eu3+and Dy3+, respectively. Tb(bda)3·5H2O don’t has luminescent property, because this ligand can’t sensitize the Tb3+Zn7O(cpda)3(OH)3shows a3D framework structure, and its crystal structure can keep stable up to400℃. Under367nm excitation, Zn7O(cpda)3(OH)3exhibits much enhanced blue luminance the H3cpda ligand.[Ln(H2cpda)(Hcpda)(H2O)]·(H2O)(Ln=Eu, Tb, Tbo.95Euo.o5) are isostructure and show1D zigzag chain structure. H3cpda can both sensitize Eu3+and Tb3+. The temperature-dependent emission spectra of [Tbo.95Eu0.05(H2cpda)(Hcpda)(H20)]·(H20) shows that the intensity ratio of546nm and615nm ITb/IEu can be linearly related to the temperature, between40to250K, indicates that we can easily and accurately get the temperature by measure the ITb/IEu·[Ln(Hdpda)(H2O)4]·0.5(H2O)[Ln=Eu, Gd, Tb, Dy, Tb1-xEux(x=0.1-10%) are isostructure and show2D layer structure. It has high thermal stability, and the host framework can be stable up to440℃. Under335nm excitation.[Tb1-xEux (Hdpda)(H2O)4]-0.5(H2O) exhibits both Eu3+and Tb3+characteristic emission. Furthermore, the luminescence color of the mixed MOFs can be easily tuned from green to green-yellow, yellow, orange, red-orange and red by varying the molar ratio of Eu3+/Tb3+...