Synthesis And Proton Conductivity Of Phosphonic Carboxylic Acid Coordination Polymers

With the development of ecological civilization construction,the development and utilization of green and clean new energy has become the focus of attention.Proton exchange membrane fuel cell technology has become a hot research topic as one of the effective and pollution-free technologies.Nowadays,Nafion membrane is widely used as the proton conducting membrane.However,it suffers from a number of short comings such as low proton conductivity at high temperature,complicated synthetic process as well as expensive price,which limits the development of fuel cells.Therefore,it is necessary to develop new proton exchange membrane materials.In this paper,a series of new coordination polymers based on phosphinic acid or carboxylic acid ligands were constructed via different synthetic methods and structurally characterized by IR,TGA and PXRD.The proton conducting properties of these coordination polymers has been studied.The main contents are as follows:1.Three phosphinic acid ligands(BMP,BDP,BTP;BMP=5-Phosphonoisophthalic Acid;BDP=3,5-Diphosphonobenzoic Acid;BTP=Benzene-1,3,5-tri(phosphonic acid)were synthesized according to the literature.Compounds 1 and 2 were prepared by hydrothermal reaction of ligands BMP and BDP with cadmium nitrate,respectively.The structures of 1 and 2 were characterized by IR and PXRD.Then thermal stability and proton conduction of 1 and 2 were tested.The proton conductivity test showed that the proton conductivity of 1 was 2.32×10-4 S·cm-1 and the activation energy was 1.06 eV under 333 K and 98%RH,which belonged to the vehicle mechanism.Under 342 K and 98%RH,the proton conductivity of 2 was 3.54×10-4 S·cm-1,and the activation energy was 0.33 eV,which belonged to the mechanism of Grothuss.2.Compound 3 was synthesized by hydrothermal method with EuCl3·6H2O and H4BDPP ligands(H4BDPP=3,5-bis(3,5-dicarboxylphenyl)pyridine).In order to further increase the proton conductivity,imidazole molecules were introduced into the channels of 3,and Im@3 was obtained.The structure of 1 and 2 has been characterized by IR and PXRD.And thermal stability and proton conduction properties were tested.At 363 K,98%RH,the proton conductivity of 3 was 1.5×10-4 S·cm-1,and the activation energy was 0.70 eV,which belonged to the vehicle mechanism.At 348 K,98%RH,Im@3 had the proton conductivity values of 4.53×10-4 S·cm-1 and activation energy was 0.17 eV,included both vehicle and Grothuss mechanism.3.Hydrogen bonded organic framework materials 4 and 5 were obtained by reacting melamine with trimesic acid and 3,5-dicarboxylic acid phenylboronic acid,respectively.The solution immersion method and the vapor diffusion method were respectively carried out,and imidazole molecules were introduced into the channels of 4 and 5,then Im@4a,Im@4b,Im@5a,Im@5b were obtained.They were characterized by IR and other structural properties,and thermal stability and proton conduction properties were tested.At 333 K,98%RH,the proton conductivity of Im@4b was 4.12×10-4 S·cm-1,and the activation energy was 0.39 eV,which belonged to Grothuss mechanism.At 353 K and 98%RH,the proton conductivity of Im@5a reached 8.37×10-4 S·cm-1,and the activation energy was 0.26 eV,which belonged to Grothusus mechanism.