Preparation And Luminescent Properties Of Lanthanide Rare Earth-organic Frameworks With Biphenyltricarboxylic Acid

Metal-Organic Frameworks?MOFs?are one type of material with a channel structure constructed of metal nodes?also known as secondary building units?SBUs??and organic bridging ligands due to their structure and function which have tunability and designability,making MOFs are one of the fastest growing areas in scientific research currently.The lanthanide rare earth-organic framework materials?Ln-MOFs?are used form MOFs with lanthanide rare earth ions as metal nodes.The lanthanide rare earth ions have excellent optical and magnetic properties and Ln-MOFs materials can be sensitized with antenna effects.The luminescence of lanthanide rare earth ions makes Ln-MOFs have higher luminous intensity,light absorption and quantum efficiency than traditional inorganic luminescent materials.Considering biphenyl tricarboxylic acid is an aromatic organic ligand of polycarboxylic acid,the polycarboxylic acid structure can provide more coordination sites with lanthanide rare earth ions than the monocarboxylic acid and dicarboxylic acid structures.The rigid structure of the aromatic rings is beneficial to increase the structural stability and further enhance the fluorescence performance of Ln-MOFs.Therefore,it is proposed to use biphenyl tricarboxylic acid as organic ligand and lanthanide rare earth ions to construct Ln-MOFs materials.Conducted a series of studies on its luminescence properties and luminescence mechanism.Using 3,4?,5-biphenyltricarboxylic acid?H₃BPT?as an organic ligand,different rare earth complexes?Eu complexes,Tb complexes,Dy complexes?in different solvents were prepared by solvothermal synthesis.La complexes),single rare earth LnBPT?Ln=Eu or Tb or Dy or La?,double rare earth LnBPT(Ln=Eu_xTb_1-x or Dy_xEu_1-x or La_xDy_1-x)and Eu_0.075Tb_0.925BPT with Py incorporated@xPy,combined with XRD phase analysis,FT-IR infrared spectroscopy,SEM energy spectrum analysis,elemental analysis,optical microscopy,fluorescence analysis and other methods to characterize the composition.Focusing on the different solvents,single rare earth,addition amounts of rare earth and Py on the phase,morphology,structure and luminescent properties of the composites were discussed.The results of the study are as follows:?1?Eu complexes,Tb complexes,Dy complexes,La complexes were prepared underdifferentsolvents?DMF?N,N'-dimethylformamide?,DMF+water,DMF+water+ethanol?.The crystal structures of the above four complexes are all prismatic crystals.Compared with DMF and DMF+water,the yield of the four complexes is the highest?about 70%yield?when the solvent is DMF+water+ethanol,which is beneficial to the growth of the crystals?The long-end of the Eu complex is 6?m¹0?m?and the most favorable for the coordination of Ln³⁺and H3BPT,and the coordination is more complete.The Eu,Tb,and Dy have the highest emission intensities in Eu complexes,Tb complexes,and Dy complexes.Therefore,it is preferable that the environmentally friendly DMF+water+ethanol is a solvothermal synthesis solvent to prepare subsequent LnBPT materials.?2?Single rare-earth LnBPT?Ln=Eu or Tb or Dy or La?materials were prepared from the lanthanides Eu,Tb,Dy,La and H₃BPT,respectively.The crystal structures of the four complexes were the same and all were prismatic crystals.In the single rare earth LnBPT?Ln=Eu or Tb or Dy or La?,the coordination forms of Eu³⁺and La³⁺are the same as that of H₃BPT,and the coordination forms of Tb³⁺and Dy³⁺are the same as those of H₃BPT.Compared with TbBPT and DyBPT,the coordination of EuBPT and LaBPT More complete;in the emission spectrum of 320 nm,EuBPT and TbBPT only have the intrinsic emission of Eu³⁺and Tb³⁺,DyBPT has both the intrinsic emission of Dy³⁺and H₃BPT,and LaBPT only has the intrinsic emission of H₃BPT,which fully shows different defects.The selectivity of the antenna effect between rare-earth ions and H₃BPT;the EuPPT emission light color prepared is basically a standard red light,LaBPT and DyBPT is very close to standard blue light point of CIE,TbBPT is close to standard green light point of CIE.?4?Double rare-earth LnPBT(Ln=Eu_xTb_1-x or Dy_x Eu_1-x or La_xDy_1-x)materials with the same crystal structure as prismatic crystals were prepared with the lanthanides EuTb,EuDy,DyLa and H3BPT,respectively.In the emission spectra of the double rare earth LnPBT(Ln=Eu_x Tb_1-x or Dy_xEu_1-x or La_x Dy_1-x)excited at 320 nm,Eu³⁺,Tb³⁺and Dy³⁺still maintain their own intrinsic emission;in Eu_xTb_1-xBPT,Tb³⁺Eu³⁺has a sensitization effect,and the emission color of Eu_xTb_1-xBPT increases with increasing Eu³⁺content?a ratio of 0:1,1:19,1:12,1:9,1:3,and 1:0,respectively?.The changes of green light?yellow?red light were observed,and high-quality yellow light was observed when the molar ratio of bismuth was 1:12;in Dy_xEu_1-xBPT,the content of Dy³⁺was increased?the turn ratio was 0:1,1:9,1:19,1:0,respectively?increase its luminescent light color red?purple?white?blue white?light blue change rule,in which the color coordinates of Eu_0.1Dy_0.9BPT is?0.3208,0.2579?,close to pure white light?0.33,0.33?;in La_xDy_1-xBPT,Dy³⁺quenched fluorescence when Dy/?Dy+La?>50%.?5?Eu_0.075Tb_0.925BPT@xPy complexes?x=2,4,5?were prepared by introducing different amounts of Py into the pores of the material.The crystal structure was the same as that of Eu_0.075Tb_0.925BPT.At 330nm excitation wavelength,Eu,Tb,and Py emit strongly in the emission spectrum of Eu_0.075Tb_0.925BPT@xPy,and Py has sensitization to Eu³⁺;the color coordinates of complex Eu_0.075Tb_0.925BPT@2Py is?0.3159,0.2816?,which is close to positive white light?0.33,0.33?.When Py and Eu_0.075Tb_0.925BPT blend ratio is 2:1 compared with the way that Py enters into the Eu_0.075Tb_0.925BPT channel,Py has no sensitizing effect on Eu³⁺in the emission spectrum,and its color coordinates is?0.288,0.332?,achieved white light emission.