Synthesis,Structure,and Luminescence Of Lanthanide Metal-Organic Frameworks Based On Lanthanide And 3,3',5,5'-Biphenyl Tetracarboxylic Acid

The lanthanide metal–organic frameworks?Ln-MOFs?are functional material with wide applica-tion value,especially in the luminescent material.In this paper,a series of novel MOFs were synthesized by reaction of biphenyl-3,3?,5,5?-tetracarboxylic acid?H₄BPTC?with lanthanide metal ion and theirs struc-tures and physicochemical properties were determined.In addition,the influences of solvents and tempera-ture on the self-assembly of MOFs were also explored.The main work is as follows:At different temperatures,the reaction of lanthanide metal oxides such as Pr₂O₃,Nd₂O₃,Y₂O₃,Gd₂O₃ with H₄BPTC,respectively,in a mixed solvent of N,N-dimethylformamide?DMF?,ethanol,water,and dilute nitric acid gives rise to four MOFs with the same structural parameters and structural formula of[Ln₃?BPTC?₃?H₂O?₂].The determined crystal structure shows that there are three metal ion centers in the asymmetric unit,in which the metal ions on two terminals are nine-coordinated mode,and the middle is eight-coordinated mode.The coordinated oxygen atoms are provided by H₄BPTC ligands and water mole-cules in the nine coordination mode,and only by the ligand in the eight-coordinated mode;Instead DMF with N,N-dimethylacetamide?DMA?at the 160? reaction conditions,the reaction of H₄BPTC with Pr₂O₃,Eu₂O₃,Nd₂O₃,Y₂O₃,and Dy₂O₃,respectively,gives five isostructural compounds with the Ln₂?BPTC?(C₂O₄^2-)₂?CH₃COO^-?₂·nH₂O formula.In the asymmetric unit of these complexs,two central metal ions are nine coordination modes and the coordinated oxygen atoms are provided by the ligand,ace-tic acid generated by decomposition of DMA,and oxalic acid obtained by further oxidation of acetic acid.However,at the 100? reaction temperature,the reaction of Eu₂O₃,Y₂O₃,Dy₂O₃,Tb₄O₇,Gd₂O₃,Ho₂O₃,Er₂O₃ with H₄BPTC give rise to seven novel MOFs with the same structural parameters and Ln₂?BPTC??CH₃COO^-?₂·2DMA·nH₂O formula,respectively.The crystal structure measurements revealed that both of two central metal ion in the asymmetric unit are nine coordinated,and the coordinated oxygen atoms are provided by ligands,acetic acid from the decomposition of DMA,DMA,and water molecules.Based on the determination of crystal structures,the physical and chemical properties of the above 16 com-plexes were characterized by XRD,TG,IR spectra and solid fluorescence spectra.Further analysis indicat-ed that DMA and DMF and their decomposed products play the different roles in the preparation of MOFs,and the effect of reaction temperature depends on the solvents of DMA and DMF.