Theoretical Investigation Of The Gas Adsorption And Separation Of The Two Kinds Of Covalent Organic Frameworks

Porous materials were first studied in the early 20 th century and are a rapidly developing material.Due to the advantages of large specific surface area,low density,adjustable pore structure,and various topological structures and chemical compositions,porous materials have a wide range of applications in catalysis,filtration,infiltration,electrochemical processes,and gas storage and separation.At present,one of the most concerned environmental issues is global warming,and the excessive emission of carbon dioxide gas from industry and daily life is the culprit of global warming.In order to effectively solve this big focus problem,it is possible to find suitable porous material storage and selected materials to absorb carbon dioxide.In addition,noble gases have a wide range of applications in the chemical industry and medical sciences due to their low boiling points,low melting points,and very stable properties.However,the rare gas is expensive,because the rare gas content is low on the earth itself,and the storage and separation of the rare gas in the production process is also a costly step.Research on the adsorption and storage of rare gases by porous materials is a solution.In this thesis,theoretical simulations are used to study the adsorption and separation of common gases and rare gases by the covalent organic framework.The specific content is as follows:?1?We selected the latest synthetic and novel series of chiral covalent organic framework?CCOF?as the research system to explore and predict the possibility of gas adsorption and separation.In this work,we explored the CO₂,CH₄,N₂,and H₂ adsorption capacity of CCOFs and investigated the CH₄/H₂,CH₄/N₂,CO₂/N₂,CO₂/CH₄ and CO₂/H₂ separating performance in CCOF4,CCOF5,and CCOF6 by the combination of Grand Canonical Monte Carlo?GCMC?simulations and DFT calculations.Due to the proper narrow channel and the charge transfer between CO₂ and CCOF6,CCOF6 shows the preferred CO₂ adsorption sites in low pressure.We find that CCOF6 is a good candidate for CO₂ adsorption and separation by comparing with other CCOFs and 4 classic porous materials.?2?Using the newly reported covalent organic framework of silicon carbide as a research system,we explored the application potential of this material in the adsorption and separation of rare gases.This skeleton is a three-layer interpenetrating structure called LZU-111.In this chapter,we use GCMC simulation to study adsorption of rare gases on LZU-111 and the separation of Kr and Ar by Xe.The materials adsorption capacity for rare gases increases from argon,krypton,xenon,krypton in order.In addition,the effect of temperature on the adsorption of rare gases by LZU-111 was studied.It was found that the higher the temperature,the smaller the amount of rare gas adsorption.Moreover,we changed the original three-layer interstitial structure of LZU-111,and changed the three-layer interpenetrating structure into a two-layer interpenetrating structure,LZU-111-2c and a single-layer structure,LZU-111-1c.In these three levels of structure,we compare the adsorption and separation of rare gases by each structure.It was found that the three-layer interstitial structure LZU-111 is more likely to adsorb larger gases,and the selectivity of Xe/Ar and Xe/Kr is also high.