Design, Synthesis And Properties Of MOFS Constructed With Nitrogen-containing Heterocyclic Carboxylic Acid Ligands

Duo to their fascinating topologies and huge potential applications in areas of gas adsorption,separation,luminescence,magnetism,catalytic,electronic and ion exchange,much research work have been devoted to designing and constructing metal-organic frameworks in recent years.And we all know that the choice of the organic linker and metal center plays a key role in the assembly of the compounds.Organic ligands containing both N and O atoms which have the stronger coordination ability were often selected to produce the complexes.And for the central metal ions,the lanthanide ions were most commonly used,because they have much higher coordination numbers and more flexible coordination geometry.In addition,lanthanide compounds can exhibit excellent photophysical properties,which can contribute to f-f transitions with an extremely narrow bandwidth.In this paper,2,3,5-pyridinetricarboxylic acid was selected as the ligand to construct seven new three-dimensional lanthanide-copper metal-organic frameworks[LnCu2(pdc)2(H2O)2]n(Ln=Sm,1-Sm;Eu,2-Eu;Gd,3-Gd;Tb,4-Tb;Dy,5-Dy;Ho,6-Ho;Er,7-Er;H2pdc=(pyridine-3,5-dicarboxylic acid))under hydrothermal conditions and part of them were characterized by IR spectroscopy,single-crystal X-ray diffraction and thermal analysis.X-ray diffraction analyses confirm that 2-Eu,3-Gd,4-Tb,5-Dy,6-Ho and 7-Er are isostructural.The central Ln3+ ion of the compounds are assembled into 1D chains by the O atom of the carboxylate of pyridine-3,5-dicarboxylic acid anion,which are further linked by two pyridine-3,5-dicarboxylic acid anions to form a 2D layer.And a 3D network is finally constructed by the Cu+ ion which is orginate from CuCN.TG study of 4-Tb,6-Ho and 7-Er shows that their framework remains stable until the temperature reached nearly 400?.Moreover,solid state luminescence of compounds 1-Sm,2-Eu,4-Tb,5-Dy,6-Ho and 7-Er were also measured.