First Principle Calculation And Molecular Dynamics Study Of Covalent Organic Frameworks

CovalentOrganic Frameworks?COFs?are novel nanoporous materials similar to zeolite structures.The organic molecular units in COFs are joined together by covalent interactions.Due to the removal of the heavier metal elements in the MOFs,it has a lower mass density,higher specific surface area and porosity.At a basic level,covalent bonds provide a way to control the integration of building blocks into pre-designed structures.These advantages combined with the strength of the connection lead to a strong material,which is currently mainly used for the storage of gases such as CH₄,CO₂ and catalysis.In this paper,the covalent organic framework of 3D and 2D structures is selected for the first principle calculation and molecular dynamics research.The total energy and molecular dynamics calculation of the covalent organic framework-112?COF-112?material adsorbing carbon dioxide?CO₂?molecules based on the first-principle method of all-electron numerical orbital basis based on density functional theory to study CO₂ molecules Adsorption binding energy and adsorption sites and adsorption surface migration mechanisms in the COF-112 framework.The results show that COF-112 is an effective CO₂ adsorption and storage material.Combined with the first-principles calculation and the multiscale method of Metropolis Monte Carlo?GCMC?simulation,the effects of doping metals and doping on the performance of CO₂ capture in porous covalent organic frameworks were further investigated.The calculation results show that doping metal elements can significantly increase the CO₂ absorption of CO2.Metals have the best modification effect on the surface of COFs,and the increase in CO₂ intake is most obvious.The adsorption properties of TPE-COFs for CO₂ and CH₄ were studied by first-principles and molecular dynamics simulations.The results show that CO₂ is more easily adsorbed on the TPE-COFs framework,and the adsorption energy and adsorption sites as well as the adsorption binding energy are much larger than CH₄,and the charge difference and orbital hybridization will occur.The difference in separation performance between CO₂ and CH₄ is mainly caused by the competitive effects of two gas molecules at different sites.The adsorption amount shown in the adsorption isotherm is obviously different.The adsorption selectivity,adsorption heat and diffusion coefficient also indicate that TPE-COFs are potential materials for selective adsorption.The gas diffusion mechanism in the separation and adsorption process is further explored by GCMC simulation.The first principle was used to calculate the catalytic reduction characteristics of TPE-COFs.The simulated COFs are considered to be effective catalysts for photolytic water reactions.Suitable energy gaps,cohesive energy,work function,edge alignment and electrostatic potential lay the foundation for the formation of H₂and O₂ in water molecules.Theoretical calculation studies not only analyze the performance of the catalyst,but also stimulate the application of 2D-COF in optoelectronics.The mechanism of chemical reaction kinetics was studied by density functional theory.The mechanism of a series of covalent organic frameworks as hydrogen evolution reaction?HER?catalysts was studied.The kinetics of HER on the surface of the framework verified the catalytic activity of HP-COFs on HER,the diffusion and migration of electrons in the catalytic process,and the active sites,indicating that HP-COFs are good catalysts for hydrogen evolution.