Design, Synthesis Of Semiconductor Materials Based On Covalent/Metal-organic Framework And Its Sensing Properties

Metal/covalent organic framework semiconductor materials have the advantages of self-assembly,solution processing,and bandgap adjustment as the active layer of electronic devices to overcome the inherent limitations of traditional silicon-based materials.It is a hot topic in the field of optoelectronic devices and sensors to arrange functional monomers at the molecular level and assemble them into two-dimensional metal/covalent organic framework semiconductor materials long-range range ordered conjugated structures through covalent bonds or coordination bonds.The continuity and stability of semiconductor materials are the basis of many sensors and electronic devices.However,metal/covalent organic framework semiconductor materials are generally prepared in a powder state,which has poor machinability.The presence of metal/covalent organic framework semiconductor materials in devices as active layers will seriously affect the stability and performance of devices.Therefore,it is of great significance and challenge to explore the ordered molecular stable structure of metal/covalent organic framework semiconductor materials and to synthesize efficient and high-quality continuous fiber films or flakes to improve carrier transport and build high-performance semiconductor optoelectronic devices.The main work of this paper is as follows:（1）Two large area two-dimensional covalent organic frame films（2D CCOF）were designed and synthesized as the active layer and photosensitive layer field-effect transistor（OFET）device and photodetector.Aryl borate porphyrins and dibromoazobenzene with strong light responses were dispersed in an organic solution with palladium catalyst as the organic phase.The amphiphilic compoupolyoxyethylenethyl-α-tocopherol sebacate（PTS）and triethylamine（Et₃N）are dispersed in water as the aqueous phase.The continuous trans（E）azobenzene/porphyrin（2D CCOF-E）and cis（Z）azobenzene/porphyrin（2D CCOF-Z）films were formed by the Suzuki coupling reaction assisted by PTS at the interface of the two phases under visible and UV light conditions,respectively.The synthesis mechanism morphology and structure of two-dimensional COF films with two configurations were fully analyzed and characterized,and the properties of the assembled devices were tested.The results show that the azobenzene molecules in 2D CCOF-Z film have cis configuration,and the molecular length of azobenzene molecules in 2D CCOF-E film is smaller than that in2D CCOF-E film,which leads to the shorter distance of charge tunneling.The organic field-effect tube of 2D CCOF-Z film has a higher carrier mobility switch ratio.At the same time,the photodetector with 2D CCOF-Z/Si has higher photoresponsivity ratio detection and switching ratio.（2）The preparation of metal-organic framework（MOF）nanofiber arrays（NFAs）and their active layer angas-sensitive layer as field-effect transistor（FET）devices and chemical resistance gas sensors are reported.PDMS-PCDA was synthesized by polycondensation of amino-terminated polydimethylsiloxane（NH₂-PDMS-NH₂）and 2,6-pyridine dicarboxylic amide（PCDA）to form a stable PDMS-PCDA/Cu coordination polymer with Cu（II）center.PDMS-PCDA/Cu nanofiber arrays were prepared by electrostatic spinning and Cu₃（HITP）₂was grown in situ on the nanofiber arrays by liquid phase epitaxy.At the same time,it is concluded that the maximum carrier mobility of Cu₃（HITP）₂NFAs FET device can be increased by 5.09 cm²V^-1S^-1switching ratio,which can reach the low threshold voltage of 9.6×10³and 2.9 V,respectively.The good linearity of the Cu₃（HITP）₂NFAs gas sensor to ethanol gas in the range of 1～20 ppm is comparable to that of the typical chemical resistance gas sensor.At the same time,the sensor for（Volatile Organic Chemicals,VOCs）at room temperature has excellent gas sensing response characteristics.（3）Two-dimensional conductive Cu₃（HHTP）₂of graphene-like was grown on the n-Si surface by liquid phase epitaxy（HHTP）.The Ti₃C₂T_x/Cu₃（HHTP）₂/n-Si heterojunction self-supplied electro-optical detector was successfully prepared by spraying the 2D Ti₃C₂T_xnanosheets prepared by etching on Cu₃（HHTP）₂/n-Si.The electron injection barrier difference between N-Si/MOF and MOF/Ti₃C₂T_xis utilized to reduce the recombination of electrons and holes at the interface and solve the problem of large dark current by using the electron-hole transfer characteristic of Type I heterostructure.The morphology and structure of the prepared 2D materials were analyzed and characterized,and the effect of the incident wavelength light source on the performance of the photodetector was compared.The Ti₃C₂T_x/Cu₃（HHTP）₂/n-Si device has a self-driven photoelectric response,and has good photoresponse performance in the UV to the visible wavelength range of 365 nm～700 nm.The maximum photoresponse rate of the device is up to 1.8 AW^-1,the specific detection is 1.63×10¹²Jones,switch ratio reaches 3.9×10⁴.