| Proton exchange membrane is the most crucial component of the fuel cell,so the research and development of high-performance proton conductive materials have become a challenging research topic.Due to the structural designability and the tunability of the channels,the metal-organic frame materials are excellent candidates for proton conduction.In this paper,we mainly studied the proton conductivity,regulation and recognition of metal-organic frameworks constructed by imidazole-4,5-dicarboxylic acid and acyl thiourea carboxylic acid ligands.The main work is as follows:（1）Considering that the imidazole and carboxylic acid groups are conducive to proton conduction of MOFs,ligands containing imidazole and carboxylic acid groups and acylthiourea carboxylic acid ligands containing a variety of functional groups were designed and synthesized.Furthermore,through the solvent-heat/hydrothermal reaction between p-IPhH3IDC and metal ions(Cu2+,Zn2+,Co2+),three heterogeneous isomorphictwo-dimensionalMOFsareobtained:[Cu（p-IPhHIDC）]n（1）,[Zn（p-IPhHIDC）]n（2）and[Co（p-IPhHIDC）]n（3）.Their two-dimensional plane forms a three-dimensional solid structure throughπ-πaccumulation.A supramolecular complex{NH4[Co2（p-IPhHIDC）4（H2O）](PMo12O40)}n（4）and a three-dimensional structure[Pb2（p-IPhHIDC）2（C2O4）]n（5）were obtained by introducing ammonium phosphomolybdate and oxalic acid as auxiliary ligands.Three-dimensional MOF,{[Cu3ICu3IIL3（DMF）2（CH3OH）（H2O）]·3CH3OH}n（6）,with one-dimensional pore structure and a large number of hydrogen bonds in the framework,was synthesized by H3L and Cu2+at room temperature.Further tests show that 1-6 has good water stability,acid-base stability and thermal stability,and can meet the proton conductivity test requirements under different humidity,100℃and certain acid-base conditions.（2）Study on proton conductivity in water vapor:for 1-6 in different humidity（68%,75%,83%and 98%RH）30-100℃under the electrical conductivity of the test.It is found that with the increase of humidity and temperature,the proton conductivity increases gradually,showing good regularity.Under the condition of 98%RH and100℃,the proton conductivity of 1-6 reached a maximum:1.50×10-33 S·cm-1,1.47×10-33 S·cm-1,1.75×10-44 S·cm-1,5.12×10-66 S·cm-1,9.16×10-66 S·cm-1,3.78×10-4S·cm-11 respectively.（3）Study on the regulation of proton conductivity:The proton conductivity of 1,4,5 and 6 were tested under different concentrations of ammonia vapor（ammonia solution concentration:0.01 M-3 M）.It was found that with the continuous increase of ammonia concentration,the proton conductivity of the complexes gradually increased,and the maximum was:（4）5.60×10-44 S·cm-1（2 M,80℃）,（5）1.15×10-4S·cm-1（3 M,100℃）、（6）5.10×10-44 S·cm-1（2 M,100℃）.Their proton conductivity also shows a temperature dependence.（4）Study on electrochemical identification performance:on the basis of the above studies,it is found that the chemical impedance of 1 is extremely sensitive to the presence of NH3.Small changes in ammonia concentration can cause large changes in impedance.Therefore,we studied the identification of ammonia vapor at68%to 98%RH.The lowest identified ammonia concentration was found to be 2ppm.At 68%RH and room temperature（25℃）of 130 ppm gas response values,the highest up to 8620%.We also studied the structural stability of these complexes during proton conduction by means of powder X-ray diffraction and scanning electron microscopy.Based on the analysis of crystal structure,the measurement of water vapor and ammonia vapor adsorption,the calculation of activation energy and the stability analysis,the proton conduction mechanism of 1-6 under different conditions was discussed. |
PDF Full Text Request