High-throughput Computational Screening Of Gas Adsorption And Separation Performance Of Covalent Organic Framework Materials

With the development of the society and economy,the greenhouse effect and fossil energy crisis have become two major problems that cannot be ignored in the 21st century.The adsorption/separation of hydrocarbons such as CH₄ and C₂H₆/C₂H₄ is a key step to obtain clean energy and reduce energy consumption.Although a lot of progress has been made in this field,there still exist such problems as low efficiency,long time consuming.Covalent organic framework（COFs）has a series of advantages,such as low density,large specific surface area,functional tunability,etc.,showing a broad application prospect in gas adsorption and separation.However,due to the increasing number of COFs materials,it is impossible to screen and analyze the materials one by one only by relying on experimental methods.Therefore,based on the databases containing h-COFs and CoRE-COFs,this paper adopts molecular simulation and machine learning（ML）to conduct a systematic theoretical study on CH₄ storage,CH₄/C₂H₆/C₃H₈ cyclic adsorption and desorption,as well as the adsorption and separation of C₂H₆/C₂H₄ of COFs materials.The main research work is as follows:（1）Methane storage capacity（65 bar）and working capacity（65-5.8 bar）of 404,460 COFs at 298 K were calculated using molecular simulation.Then five ML algorithms including gradient boosting decision tree（GBDT）,neural network（NN）,support vector machine（SVM）,random forest（RF）and decision tree（DT）were used to construct the model and evaluate the prediction ability of the model.The results show that RF model had the highest prediction accuracy,and and DT model can successfully identify high-performance materials from the database with an accuracy of more than 97%.The working capacity of the screened COF is superior to the various adsorbents reported so far.The results provide some guidance for the design and synthesis of new methane storage materials.（2）To study the effect of ethane and propane on the performance of adsorbed natural gas（ANG）storage tanks,we established a mathematical model to describe the state of ANG tank at any time based on the GCMC simulation,the theory of ideal adsorbed solutions（IAST）and the law of conservation of mass.We focused on the accumulation of impurities in 160 COFs.It was found that the performance of ANG tanks declined monotonically in the early operating cycle until a stable state was reached in any COF,and COF-A was the best-performing material.This provides guidance for the design and synthesis of materials in practical situations.（3）In this study,534 different CoRE-COFs were selected by molecular simulation on a large scale to study the adsorption and separation properties of C₂H₆/C₂H₄ isomolar mixtures,and the adsorption selectivity,working capacity and adsorbents selection parameters of COFs were evaluated.Through the analysis of the structure-performance relationship,the structural features of the ideal separation materials are excavated.At the same time,some high-performance materials which can be used for C₂H₆/C₂H₄ separation are screened out,which provides theoretical guidance for the further design and synthesis of high-performance COFs.