| With the rapid progress of electronic industry technology,electronic devices are gradually developing towards high performance,intelligence and integration,and higher requirements are placed on the materials for preparing electronic devices.MOFs materials are porous materials with periodic network structure assembled by different metal nodes and organic ligands.Due to their advantages of permanent porosity,adjustable pore size,designable structure,high surface area,porosity and conductivity,they have broad application potential in the manufacturing of intelligent electronic devices in recent years.Most of the MOFs materials exist in the form of powder,which limited their integrationg and application in diverse electronic devices.In order to solve this problem,design and preparation of different MOFs thin films has attracted the attention of many researchers.Among them,the method of growing MOFs thin films on the surface of various hard substrates such as silicon wafers,ITO thin films and other materials has been proposed,but the mechanical flexibility and processability of hard substrates are poor.Therefore,developing a synthetic method of MOFs thin films based on flexible polyester fiber can not only realize the integration with electronic devices,the advantages of flexible thin films,such as bendability,air permeability and light weight,can also meet the needs of various flexible electronic devices.Meanwhile,the conductivity of the material is crucial for the transmission and conversion of electronic information in electronic devices.Most MOFs materials have low conductivity due to the poor overlap of the orbitals of metal ions and ligands.The post-synthesis modification method can solve this problem,that is,introducing different guest molecules into the pores of MOFs to modify metal nodes and ligands can tuning their conductivity.In this thesis,polyester fiber-based Cu-BTC,Cu-HHTP and Cu-DOBDC flexible films were prepared,and different guest molecules were introduced into the pores of MOFs materials by post-synthesis modification and their conductivity were obviously improved.The research content mainly inclueded the following three aspects:(1)The surface modification of polyester fiber was carried out by atomic layer deposition technology.A layer of alumina film was deposited on the surface.Its rich hydroxyl sites can effectively improve the binding force and uniformity of polyester fiber surface and MOFs film.Cu-BTC thin films with controllable thickness can be prepared by layer-by-layer liquid phase epitaxy(LBL),and the thickness depends on the number of LBL cycles.In the Cu-BTC flexible film,7,7,8,8-tetracy anoquinodimethane(TCNQ)and polypyrrole(PPy)were introduced as guest molecules to improve the conductivity.The conductivity of TCNQ@Cu-BTC increased by 4 orders of magnitude,and the conductivity of PPy@Cu-BTC increased by 5 orders of magnitude.The mechanism of doping conduction is revealed.After TCNQ enters the channel,it binds to the copper site of the paddle wheel structure in Cu-BTC,and charge transfer occurs between the host-guest to improve the efficiency of charge transfer.In PPy@Cu-BTC,the conductive polymer PPy polymerizes in situ in the interconnected pores of CuBTC to form a new charge conduction path.The TCNQ/PPy@Cu-BTC film not only has good electrical conductivity,but also has excellent bending and folding resistance.It is a promising flexible porous conductive material.(2)By improving the preparation method of flexible MOFs film,the flexible Cu-HHTP film was prepared by self-sacrificing template method.A uniform copper layer was deposited on the surface of polyester fabric by magnetron sputtering.The copper layer was converted into copper hydroxide nanowires,and then reacted with the ligand to obtain Cu-HHTP film with uniform thickness and firm binding.The guest molecule iodine(I2)was innovatively introduced into the channel of 2D MOFs Cu-HHTP to further improve the electrical properties.The conductivity of I2@Cu-HHTP depends on the doping time.As the doping time increases from 0 to 72 h,the conductivity increases first and then decreases,reaching a maximum at 48 h,and the conductivity increases by about 34 times.Further characterization reveals the mechanism of conduction.The iodine molecules adsorbed in the pores interact with the functional groups on the pore wall of Cu-HHTP,resulting in the improvement of electrical properties,while excessive iodine molecules hinder the transport of electrons,resulting in the reduction of electrical properties.The I2@Cu-HHTP film has the properties of bending and folding resistance,and the conductivity of the sample remains stable for up to four months in air.(3)In order to explore the universality of the self-sacrificing template method,the reaction conditions of the self-sacrificing template method were further optimized,the effect of reaction time on the morphology and structure of Cu(OH)2 NWs,and the effect of ligand concentration on the crystallinity of MOFs were investigated,and the flexible Cu-DOBDC film was successfully prepared.The intrinsic conductivity of Cu-DOBDC was extremely low,and TCNQ guest molecules were introduced into its 1D pores to induce the material to produce higher conductivity.After doping,the conductivity of the material increased by 4 orders of magnitude,reaching 3.4×10-2 S/cm.The conductivity of TCNQ@CuDOBDC film is related to the exposure time of MOF in TCNQ solution.As the exposure time increases from 0 to 72 h,the conductivity gradually increases,which conforms to the percolation theory.The mechanism of conductivity improvement was revealed.It is TCNQ that formed a local conductive region inside Cu-DOBDC.When the adsorption amount of TCNQ reaches a certain value,the local conductive regions will connect with each other to form an overall conductive network.As a result,the conductivity of the material increases by 4 orders of magnitude.TCNQ@Cu-DOBDC film combines porous,conductive and flexible properties,and has a wider range of applications in flexible electronic materials. |
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