Preparation And Characterization Of Conductive Polymers And Metal-organic Frameworks Composites

Common conductive polymers include polypyrrole,polyaniline,polythiophene and other conductive polymers.Due to their long chain of conjugated structures,polymers can provide conductive carriers and have good charge transfer capability.After the polymer have been doped,their conductivity can rise several orders of magnitude increase in the super capacitor,sensor,solar cell,conductive composite materials,the doped polymers have a wide range of applications.Recent studies have shown that the presence of conductive polymers have a close relationship with their better properties,so the preparation of conductive polymers in a particular state of existence is of great importance to their performance.Few Mental-Organic Framework materials(MOFs)are conductive due to the electron transport.Therefore,in this paper,MOFs are used to synthesize conducting polymers in their nano-pores to improve their conductivity.Metal-Organic Frameworks were used as templates to synthesize conductive polymers in their highly ordered nano-pores by chemical oxidation.A series of characterization and performance studies on the as-prepared conductive polymers/metal-organic framework composites heve been carried out.Firstly,PPy@Cu-BTC and PPy@In-BDC composites have been synthesized by the chemical oxidation method using Cu-BTC with the three-dimensional channels and In-BDC with the one-dimensional channels as the templates respectively.In the linear scanning test,the results show that the electrical conductivity of PPy@Cu-BTC composite prepared in the three-dimensional MOF tunnel is 9.8×10-5 S/cm.Compared with the electrical conductivity of MOF template,bulk PPy(about 10-8 S/cm)and polypyrrole(about 10-8 S/cm)after template removal,the electrical conductivity of PPy@Cu-BTC composite rises by at least four orders of magnitude.Similarly,PPy@In-BDC composites have been synthesized in one-dimensional MOF channels with conductivity of 7.2×10-5 S/cm,which was significantly higher than those of MOF,bulk polypyrrole and polypyrrole isolated from the PPy@In-BDC composite.From these results,we can see that the polypyrrole long chains are encapsulated in the MOF pore channels in an orderly manner by either electron transfer or π electron interaction with the pore walls,either in one-dimensional or three-dimensional MOF channels.Because of electronic transmission between the polypyrrole long chain and pore wall under the action of an electric field,compared to the synthesis of disordered polypyrrole in solution,the conductivity of PPy@Cu-BTC composites heve been greatly improved.Secondly,we use MIL-101 with three-dimensional channels and one-dimensional channels of In-BDC as the templates respectively and realize the oxidative polymerization of 3,4-divinyldioxythiophene(EDOT)in the channels.Through X-ray powder diffraction,scanning electron microscopy,thermal gravimetric analysis,N2 adsorption and infrared analysis,two composite materials analysis,PEDOT@In-BDC and PEDOT@MIL-101 were successfully prepared.The conductivity of PEDOT@In-BDC reachs 2.7×10-5 S/cm by linear scan test,and the conductivity of the composite is at least six orders of magnitude higher than that of functional In-BDC template.The conductivity of PEDOT@MIL-101 composites is 2.8×10-5 S/cm.The results show that the PEDOT@MOF composites are uniform in electrical conductivity,whether synthesized in a one-dimensional or three-dimensional MOF channels.Due to the insulating nature of the MOF templates,both PEDOT@In-BDC and PEDOT@MIL-101 composites are a class of semiconducting materials based on PEDOT.Finally,the pyrrole was chemically oxidized and polymerized in the nanopore with the porous material CYCU-3 as a template to obtain the porous PPy@CYCU-3 composite.The structure of CYCU-3 remained stable and the morphology did not change during polymerization throughout the pyrrole pore.The resulting PPy@CYCU-3 composite has a BET up to 420 m2/g with a certain degree of porosity.The conductivity of the porous composite reached 5.1×10-7 S/cm,which was significantly higher than that of CYCU-3(σ≈10-13 S/cm)by six orders of magnitude,which improved the conductive properties of CYCU-3,the composite material is a semiconductor material.This material is porous and electrically conductive and can be used as a functional material in environmentally friendly materials.Double-hole In-BDC was used as a template and the method of spirobifluorene(SBF)plugging was used.After pyrrole polymerization,SBF was eliminated to obtain a conductive PPy@In-BDC composite with a certain number of pores.The study found that the amount of SBF entering the In-BDC channel was about 35%accounts for the total weight of SBF@In-BDC.The resulting[SBF+PPy]@In-BDC composite has a conductivity of 3.1 ×10-3 S/cm,while the conductivity of PPy@In-BDC composite is about 7.2×10-4 S/cm,both of which are good semiconductor materials.However,due to the uncertainties such as the influence of spirobifluorene existencing form in the channels on the pore structure,the porosity of PPy@In-BDC composites remains to be further studied.