Synthesis And Ion/Temperature Sensing Of Eu-based Metal-Organic Frameworks

Owing to the advantages of adjustable pore size,designable function,excellent thermal and chemical stability,convenient synthesis process,Metal-Organic Frameworks(MOFs)posess tremendous potential applications in gas storage&separation,catalysis,chemical&physical sensing,drug delivery,proton conduction,optoelectronics,imaging and other fields.Among them,the luminescent MOFs are widely reported in the ares of ions detection and temperature imaging because of its rich luminescence sites of metal ions,organic ligands and guest molecules,adjustable structure,and host-guest interaction.Under the circumstances of increasingly serious environmental pollution,the research of specific probes for pollutant ions with high sensitivity has a timely significance.Besides,real-time accurate detection in different temperature range is also a very urgent demand in the fields of scientific research,industrial application and biomedicine.In this paper,a new type of rare earth metal-organic framework material Ln3(TCPE)2(?-OH)(H2O)16·0.5DMF(LnTCPE,Ln = Eu3+,Yb3+,Gd3+,Er3+,Nd3+)with three-dimensional periodic structure was synthesized by solvothermal method using organic ligand H4TCPE(1,1,2,2-Tetra(4-carboxylphenyl)ethylene)and rare earth nitrates.EuTCPE can specificly recognise MnO4-ions with transient response,low detection limit,high sensitivity,and good anti-interference ability to other anions,which can be used as a fluorescent probe for detecting MnO4-ions in water.Based on the advantage of the designable luminescent sites of luminescent metal-organic framework materials,a red dye molecule DMASM was introduced into EuTCPE as a new luminescent center leading to a composite DMASM@EuTCPE.This material showed a good temperature sensing performance in the range of 20-2000C with high relative sensitivity and good repeatability,as the fluorescence intensity(I630/I467)shows a good exponential relationship with the temperature change.Thus DMASM@EuTCPE can be a good self-calibrated fluorescence temperature probe in the range of 20-200 ?.We also prepared a rare earth metal-organic framework Eu-bpdsdc based on the ligand H4-bpdsdc(Biphenyl-3,3'-disulfonyl-4,4'-dicarboxylic Acid).Under the excitation of UV at 393 nm,the ligand H4-bpdsdc can effectively sensitize the characteristic emission of Eu3+(5D0?7FJ,J= 0-4).The C460@Eu-bpdsdc composite with double luminescent center was successfully obtained by encapsulating 7-diethylamino-4-methylcoumarin(C460),a blue emitting fluorescent dye,into Eu-bpdsdc.Under the excitation of UV at 389 nm,the characteristic emission intensity(I448)of dye C460 and the characteristic emission intensity of Eu3+(I618)decreased with the increase of temperature.However,the rate of descent is different thus the intensity ratio I448/I618 showed a good linear relationship with the temperature.Therefore,self-calibrated fluorescence temperature detection can be carried out in physiological temperature range of 20-60 ? with high relative sensitivity and good repeatability performance.