Syntheses,Structures And Properties Of Rare Earth And Transition Metal-Organic Frameworks

Now the research of metal organic framework?MOFs?is a hot topic in material and chemistry sciences for their appealing skeleton structures and potential applications,such as gas separation and storage,catalysis,drug delivery,sensing,luminescent materials and molecular magnetism and et.al.Among the investigations of applications,many efforts have been devoted to the development of luminescent MOFs,which can be used for in the detection of explosive materials and organic pollutants in the air and the removal of heavy metal ions and organic dyes in the water system.In the assembly of MOFs with specific chemical and physical properties,the proper selection of metal centers and organic ligands plays an important role.Aromatic carboxylic acids,as the tipycal ligands in the constructions of MOFs,have different interactions and supramolecular coordination mode,such as hydrogen bonding interactions and ? … ?stacking interactions.Therefore,they are excellent ligands to construct various MOFs.Recently,more and more explaration has been paid to polycarboxylic acids,for example,three compounds such as 2,6-naphthalenedicarboxylic?2,6-H₂NDC?,2,2',4,4'-biphenyltetracarboxylic acid?2,2',4,4'-H₄BPTC?and 2,3',4,5'-biphenyltetracarboxylic acid?2,3',4,5'-H₄BPTC?are tried in the MOFs assembly in this paper.2,6-H₂ NDC has various coordination modes,high symmetry and structural rigidity,thus it can be used as an excellent bridging ligand to construct MOFs with good topological structures and unique properties.Compared to the 3,3',5,5'-H₄ BPTC which is of great concern in the domain of MOFs,2,2',4,4'-H₄ BPTC is still undeveloped.The steric effect between the 2-and 2'-carboxylate groups make a benzene ring with respect to another ring being twisted,so 2,2',4,4'-H₄ BPTC can be viewed as a twisted?-shaped organic secondary building unit?SBU?.Such a unique SBU,combined with different inorganic SBUs with various geometries,may lead to the formation of MOFs with unique topologies.2,3',4,5'-H₄ BPTC has lower symmetry and unique coordination modes.However,MOFs built by 2,3',4,5'-H₄ BPTC have rarely been reported.In addition,the introduction of second ligand is also an important method to construct new MOFs with high-dimensional structure.The main results of this paper are as follows:1.Eight new isostructural 3D rare earth metal-organic frameworks{[RE₂?NDC?₃?H₂O?₄]·?DMF?₄}n?RE = Eu?1?,Gd?2?,Tb?3?,Er?4?,Yb?5?,Dy?6?,Y?7?,Lu?8?,H₂ NDC = 2,6-Naphthalenedicarboxylic acid,DMF =N,N-dimethylformamide?have been successfully synthesized under solvothermal conditions,using the rigid 2,6-H₂ NDC ligand as organic ligand and rare earth element as metal center.The topology analysis shows that it is a2,4,5-connection network,and its Sch?fli symbol is?42.62.82?2?42.63.85?2?6?calculated by TOPOS 4.0.In the studies of the products,all the compounds 1-8show good thermal stability and solvent stability.Compounds 1,2,5,7,8,exhibit good luminescence properties.Compound 1 shows good sensing properties for small molecules of organic solvents.This result shows 1 can be used to detect small molecule organic pollutants.2A activated product of 2exhibits good adsorption capacity for four kinds of organic dyes?crystal violet,methylene blue,rhodamine B,methyl orange?in water,especially for crystal violet.This results means the 2A can be used to remove organic dyes in aqueous solution.This work shows that the prepared RE-MOFs have potential applications in luminescent materials,especially in chemical sensing and luminous thermometer.?second chapter?2.Using the rigid ligand 2,6-H₂ NDC as organic ligand and the 4,4'-bipyridine as the second ligand,a 1D chain structure[Zn₂?4,4'-Bipy??CH₃COO?₄H₂O]?compound 9?has been successfully synthesized under solvothermal conditions.Using 2,2',4,4'-H₄ BPTC and2,3',4,5'-H₄ BPTC as organic ligands and transition metal zinc as metal center,a2 D layered structure H₄[Zn₅?BPTC?₂O₂?OH?₂?H₂O?₄]?compound 10?and a 3D mesh structure [Zn?H₂BPTC?]n?compound 11?have been constructed under hydrothermal conditions.The compounds 9-11 have good luminescence properties which means compounds 9-11 may be a possible application in luminescence.