| Porous metal-organic frameworks which always show higher BET surfaces and regular channels make a great break through in designing the nteworks with kinds active sites compared with inorganic materials and become a research hotspot. Based on the structures and various properties of porous materials, we foucus our attempt on the synthesis, structures, functional properities and modification the performances of lathanide metal-organic frameworks(Ln-MOFs), which are constructed by the pyridine carboxylic ligand. We have synthesized 22 Ln-MOFs that could be classified into three groups:(i) constructed by 5-(4-carboxyphenyl)picolinic acid(H2CPPA) and lanthanide ions under the solvothermal condition, we got 14 Ln-MOFs, single-crystal X-ray analysis reveals that all the structures are isomorphic, Ln-MOFs-1 shows a 2D undulate sql(44.62)layer and the 3D was formed through the connection of H-bonds between adjacent layers, the whole structure contains 19.5% solvent accessible voild, connected hydrogen bonded topological net with the point symbol of {42.6}2{44.62.88.10};(ii) by changing the synthesision conditions we got another 4 isomorphic 3D network frameworks which could be simplied into 2-nodal(3, 12) with point symbol(420.628.818)and there are 40% free volume among the networks calculated by Platon;(iii) an other four isostructural Ln-MOF have been synthesized by 2, 5-di(3’, 5’-dicarboxylphenyl)pyridine(H4DPP) and Sm3+/Eu3+/Tb3+/Dy3+ under the solvothermal conditions, single-crystal X-ray analysis reveals that 3D structures contain two kinds of holes due to the different coordination styles of oxalic acid, the porosity of this kind of materials is 37% calculated by Platon, and TOPOS analysis shows that it is 2-nodal(5, 6) with point symbol {43, 66.8}2{46.69}.Different kinds or coordinationed styles of pyridine-carboxylate ligands cloud provide new active sites which would have influence on fluorescence properties of frameworks.Eu3+and Tb3+ based frameworks have been used to sense the metal cations, the frameworks could detect the Fe3+ among kinds of other cations, it offers a great way for us to detect the amount of Fe3+ accurately, as for the relationship between the intensity of emission peaks and concentration of Fe3+ has been determine by the nonlinesr fitting. What is more interesting is Ln-MOF-8 could sense Fe2+ and Cu2+ as well as Eu3+ and Dy3+, it is the first time that Eu3+ and Dy3+ could be reported by an other lanthanided based frameworks. The experimental results show that the principles of the sensor could be from three points:(i) metal cations exchange with the hosts and interact with the networks to enhance or restrict the properties of fluorescence;(ii) the metal ions inter with active sites from metal center or oxygen;(iii) the metal ions could interactive with the N atom from the organic ligands.In-situ growth of nano-Ag particals in the channels of metal-organic frameworks provides a great way for us to modification the porperities of the porous materials. Experiments relveal that the catalyst capability of this kinds of composity materials is much better than the single Nano Ag particles and anionic frameworks show a excellent properties of catalysis due to the convienience ions exchange of hosts and Ag+ ions. |
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