Design,Synthesis And Proton Conduction Properties Of Nitrogen-Containing Functional Organic Polymer

Proton conduction is originally a biological concept,which refers to the transport of proton（H+）through the membrane.Later,it was used to proton-exchange membrane fuel cell,which refers to the process of H+ionized by hydrogen passing through the membrane.At present,it has been widely used in protonic field effect transistor,proton memristor and electrochemical sensor.People also put forward higher requirements on the stability,proton conduction performance and universality of proton conduction materials.Polymers containing a large number of nitrogen atoms have important research significance in proton conductivity and stability.In this paper,based on the design and synthesis of nitrogen-containing functional organic polymers,a series of nitrogen-containing organic polymers were prepared by using nitrogen-containing organic precursors.Single crystal X-ray diffraction（XRD）,powder X-ray diffraction（PXRD）,fourier transform infrared（FT-IR）spectroscopy,thermogravimetric analysis（TGA）and electrochemical impedance spectroscopy（EIS）were used to study their structure,proton conduction properties and mechanism.This paper mainly includes the following three parts:（1）Using cyclohexane-1,2,4,5-tetracarboxylic acid as precursor,the supramolecular organic polymers NOP-1 and NOP-2 were prepared by solvothermal method with nitrogen-containing guanidine carbonate and melamine,respectively.Both materials have good crystallinity.Single crystal X-ray diffraction analysis showed that NOP-1 has 14.8×4.9（?）of rhombic channels,while NOP-2 has no regular pore structure.In terms of proton conductivity,NOP-1 has a good hydrophilicity and regular pore structure,showing a proton conductivity of1.03×10^-2 S cm^-1 at 80℃and 98%relative humidity（RH）,but NOP-2 does not show obvious proton conductivity under the same test conditions.This comparison shows that the pore structure and hydrophilic groups of the materials are conducive to the introduction of water molecules,which improves the density of active protons and proton carriers,and makes the materials have better proton conductivity.The experimental results provide a new idea for the design and development of proton conducting materials.（2）Using biphenyl-4,4-diphosphonic acid as precursor,the supramolecular organic polymers NOP-3 and NOP-4 were prepared by solvothermal method with guanidine hydrochloride and 1,2,4-triazole,respectively.The two materials also have good crystallinity.Single crystal X-ray diffraction analysis showed that NOP-3 and NOP-4 had similar crystal structures.After loading phosphoric acid,the nitrogen element of the two crystals almost disappeared and changed into the same structure.Elemental analysis and infrared spectroscopy showed that guanidine ion and 1,2,4-triazole are replaced by phosphoric acid in two crystal structures.Therefore,more ordered proton conduction pathways are constructed and the density of active protons and proton carriers increase.When the temperature is 80℃and the relative humidity is 98%,the crystal of phosphoric acid shows 2.97×10^-2 S cm^-1,which is four orders of magnitude higher than that before loading.The transformation of crystal structure proves that the material can introduce phosphoric acid into the framework based on the stimulation response,thus improving the proton conductivity of the material.This work provides more possibilities for the design of proton conducting materials.（3）The precursor 2,3,6,7,14,15-hexaaminotriptycene（THA）was synthesized from triptycene and reacted with 2,4,6-triformylphloroglucinol to obtain a nitrogen-containing organic polymer NOP-5.AC impedance measurement shows that NOP-5 has very low intrinsic proton conductivity.When NOP-5 was loaded with phosphoric acid and sulfuric acid respectively,both of them showed excellent proton conductivity.Under 80℃and 98%RH,The proton conductivity of NOP-5-H₃PO₄ can reach 1.19×10^-1 S cm^-1,and the value of NOP-5-H₂SO₄ can reach 2,47×10^-1 S cm^-1 under the same condition,which is about 5 orders of magnitude higher than that before loading.The results show that the loading of inorganic acids can effectively enhance the proton conductivity of organic polymers.It has reference significance for the design and improvement of polymer-type proton conducting materials in the future.