Preparation Of Two-dimensional Materials Containing Viologen Structure And Their Photoelectric Catalytic Performance

Since the discovery of graphene in 2004,the preparation and application of new two-dimensional materials has been an important frontier in the field of materials research.Thanks to the quantum confinement effect in the thickness direction of the atomic layer,these two-dimensional materials exhibit completely different properties from their corresponding three-dimensional structures.Therefore,high-quality controllable two-dimensional materials are very important for exploring new physical phenomena and properties under the two-dimensional limit,and have many novel applications in the fields of photonics,electronics,batteries,and drug transportation.It is of great significance to create a new type of optoelectronic functional two-dimensional material.This thesis mainly studies the construction and catalytic performance of two types of two-dimensional materials based on viologen building units.The first part of the work is mainly to design and synthesize the viologen structure molecule PzV-Cl₂ with coordination function,and prepare an asymmetric Janus membrane material by coordinating with Au（tht）Cl on the liquid-liquid interface.On one side of the membrane,the ligands of the viologen structure coordinate with gold to form a network structure,and on the other side are gold nanoparticles（AuNPs）.The morphology and thickness of Janus film and the size of gold nanoparticles were characterized by field emission scanning electron microscope and atomic force microscope system.The results of thin-film solid ultraviolet experiments show that there are characteristic absorptions of gold nanoparticles and viologen structure in the ultraviolet spectrum.The cyclic voltammetry graph shows that the Janus film has the same two pairs of redox peaks as viologen.In addition,due to its unique heterojunction structure,Janus film shows good photocurrent behavior（stability up to more than 800 s）and photocatalytic decomposition of aquatic H2 performance.This study opens up a new way for the controllable preparation of two-dimensional Janus films with different functions of AuNPs..The second project is the preparation of two-dimensional COF materials based on 1,1’-bis（4-aminophenyl）-4,4’-bipyridine dichloride and 2,4,6-trihydroxy-1,3,5-benzenetricarbaldehyde by heating aluminum blocks.COF-Al-Block-Cl2 was synthesized by Schiff base reaction with viologen as precursor.COF-Al-Block-Cl2 was characterized by condensation of amino and aldehyde groups by infrared spectroscopy and solid state NMR.In addition,the crystallicity and chemical environment of COF-Al-Block-Cl2 were characterized by X-ray photoelectron spectroscopy and X-ray powder spectrometer.The morphology of COF-Al-Block-Cl2 was characterized by field emission scanning electron microscopy and field emission projection electron microscopy.The morphology of COF-Al-Block-Cl2 was in micrometer flower shape.The crystal lattice fringes were also observed,which indicated that the crystal was crystalline.BET and pore size distribution data shows that COF-Al-Block-Cl2 has a good adsorption curve and pore size distribution of 1.26nm.Based on the advantages of COF-Al-Block-Cl2,it is also a member of carbon and nitrogen materials.COF-Al-Block-Cl2 as metal-free electrocatalyst was used for ORR in combination with the advantages of cyanine structure compounds and carbon and nitrogen materials.At present,precious metal catalyst groups are the main catalysts for ORR reaction.The application of precious metal catalyst is hindered by high price and limited storage.COF-Al-Block-Cl2 as a high performance and low cost metal-free electrocatalyst is expected to replace the expensive platinum or platinum based alloy electrocatalyst.COF-Al-Block-Cl2 exhibited good ORR catalytic activity in alkaline media due to its high specific surface area,excellent porosity and exposed active site of pyridine N.It indicates a starting potential of 0.8V（VS RHE）and a high diffusion limiting current density of 4.6 mA cm-2.It shows long-term stability,good 2-electron oxygen reduction（n=2.3）,current efficiency and high H2O2 selectivity（>80%）in alkaline medium.These results make COF-Al-Block-Cl2 a candidate material for ORR as an effective electrocatalyst for hydrogen peroxide production.Due to the excellent photoelectric properties of viologen molecules,the constructed two-dimensional materials have very promising applications in the fields of electrochromism,energy storage,and catalysis.At the same time,positive charge characteristics of the viologen molecules,the charge on the surface of the material interacts through electrostatic repulsion,reducing the accumulation of two-dimensional material layers,which is beneficial to the preparation of single-layer or few-layer two-dimensional materials.In this study,two types of two-dimensional materials containing viologen molecules have been constructed by different methods.