| Covalent organic frameworks（COFs）are two-dimensional（2D）or three-dimensional（3D）reticulated porous polymers with long-range ordered periodic structures formed by the precise assembly of covalent bonds between organic building blocks.Compared to other porous materials,COFs have the advantages of abundant porosity,low density,high specific surface area and pore volume,and excellent stability.The nitrogen-rich covalent organic frameworks materials are rich in nitrogen and therefore have a wide range of applications in photocatalytic hydrogen production,iodine adsorption,organocatalysis,and CO2 storage and separation.In this paper,three nitrogen-rich covalent organic frameworks were constructed using a solvothermal method,and the corresponding structural simulations were carried out using Materials Studio software.The paper also explores the diverse applications of nitrogen-rich covalent organic frameworks under different conditions.The paper consists of the following main parts:In the first chapter,the development of covalent organic frameworks materials,the main synthetic methods,and applications are firstly briefly introduced.Secondly,the development of nitrogen-rich covalent organic frameworks materials is highlighted,and the advantages of their properties and structures compared to other covalent organic frameworks materials as well as their latest developments are discussed.Finally,the significance and purpose of the research in this paper are presented.In the second chapter,firstly,we used 5,5’,5’’-（1,3,5-triazine-2,4,6-triyl）tris（pyridine-2-amine）（TPTA）with 2,5-dihydroxyterephthalaldehyde（DHTA）as the building blocks and obtained pyridine-rich two-dimensional covalent organic frameworks（DHTP-COF）by a solvothermal method.Secondly,DHTP-COF was investigated for the application of carbon dioxide adsorption at different temperatures,and the results showed that the adsorption of carbon dioxide by DHTP-COF was 1.69mmol·g-1 and 0.86 mmol·g-1 at 0°C and 25°C,respectively,and its adsorption sites were simulated theoretically using Materials Studio software.Finally,the effect of the structure of DHTP-COF on the adsorption performance of carbon dioxide was investigated.In the third Chapter,we prepared a nitrogen-rich two-dimensional covalent organic frameworks（TPTF-COF）using two organic monomers,TPTA and 5,5’,5’’-（1,3,5-triazine-2,4,6-triyl）triphenylaldehyde（TFPT）.The solid UV spectra showed strong absorption between 200 and 600 nm.The band gap of the TPTF-COF was calculated to be 2.68 e V based on the absorption spectrum.the criteria for photocatalytic hydrogen production withΔE>1.23 e V were met.The photocatalytic hydrogen production efficiency of TPTF-COF under different electron sacrificial agents was investigated and found to be 1.66315 mmol·g-1·h-1 in the triethanolamine system and the mechanism was analysed.In the fourth Chapter,we prepared fully conjugated covalent organic frameworks（FC-COF）using TPTA,TFPT and 1-naphthalene cyanide as reactants via the Groebke-Blackburn-Bienayméreaction and characterised their structures using PXRD and IR spectroscopy.The results show that FC-COF has some crystallinity.The stacking mode of FC-COF was determined to be AA stacking by Materials Studio data simulation. |
