Synthesis And Properties Of Aromatic Polycarboxylate-based Lanthanide Metal-organic Frameworks Regulated By DMF And DMAc

Lanthanide ions have special optical,electrical and magnetic properties due to their unique 4f electronic structure.At the same time,the larger ionic radius enables the synthesized metal-organic frameworks to have higher coordination numbers.Therefore,lanthanide metal-organic frameworks（Ln-MOFs）not only possess the properties of lanthanide ions,but also characteristics common to all MOFs.It is of great significance for the research of multifunctional MOFs materials to prepare Ln-MOFs with excellent performance and diverse structures and explore their applications in the fields of luminescence,conductivity,magnetism,gas adsorption and separation,fluorescence sensing,catalysis,etc.By using aromatic tetracarboxylic acid 1,2,4,5-tetrakis（4-carboxyphenyl）benzene（H₄TCPB）reaction with lanthanide nitrates,a series of three-dimensional Ln-MOFs（1-4 and 5-8）and one-dimensional Ln-MOFs（9-10）were synthesized through the hydrothermal/solvothermal method.The single crystal structure determination shows that 1-10 are all crystallized in the triclinic system P（?）space group,and 1-8 are the anionic framework of the three-dimensional structure.The dimethylamine cation in the structure 1-4 is formed by the decomposition of DMF,and the dimethylamine cation in the structure 5-8 is formed by the decomposition of DMAc.9-10 are neutral lanthanide metal-organic frameworks with one-dimensional structures.The flexible coordination modes of carboxylic acids make the 1-10 structures diverse.The coordination modes of the carboxylic acids on the ligands in 1-8 are monodentate（μ₁-η¹）and cis-cis bidentate（syn-syn-μ₂-η¹:η¹）.The coordination modes of the carboxylic acids on the ligands in 9-10 are monodentate（μ₁-η¹）and chelating（μ₁-η¹:η¹）.At the same time,basic characterization and detailed analysis of 1-10 are carried out,and their functions are studied,and the main research results are as follows:Four novel lanthanide metal-organic frameworks were synthesized using N,N-dimethylformamide（DMF）as solvent,and their basic structures were characterized.Topological analysis shows that 1-4 have the same topology,both are 4-8 connected flu topology.Fluorescence tests showed that both metal-organic frameworks 1 and 3 had good selective recognition for salicylaldehyde,with detection limits of 0.095 ppm and0.043 ppm,respectively.In addition,1 can also be used as a ratiometric fluorescence sensor to identify PO₄^3-and HPO₄^2-in water with detection limits of 0.165m M and0.139m M,respectively,and 3 can also identify Fe³⁺with a detection limit of 0.076m M.Six novel lanthanide metal-organic frameworks were synthesized using N,N-dimethylacetamide（DMAc）as solvent,and their basic structures were characterized.Among them,5-8 belong to isomorphism,and 9-10 belong to isomorphism.Fluorescence tests show that the solid-state emission of metal-organic frameworks 5,7,8,and 9 all have characteristic emission peaks of rare earth ions,in which the ligands sensitized the luminescence properties of 5,7,and 9 through the antenna effect.5-8 has a rich hydrogen bond network,and the conductivity test shows that the proton conductivity of 7 is 3.298×10^-7 S·cm^-1 at 70°C and 98%RH.