Genomics-guided Computational Screening And Design Of New Gas Separation Materials

As an important chemical raw material,the separation and purification of ethylene(C2H2)plays an important role in chemical industry.In addition,sulfur hexafluoride(SF6)is a very widely used insulating gas while its emission can cause a strong greenhouse effect,thus separation and recycling of this substance is of great significance from a viewpoint of environmental protection.Metal-organic frameworks(MOF)have attracted great attention in the fields of gas adsorption and separation due to their high porosity,high specific surface area and adjustable size.In view of the variety of the types and structures of such materials,962 MOFs containing Cu2(COO)4 paddlewheel-like secondary inorganic structural unit were collected in this thesis from the Cambridge Crystal Structure Database(CSD),under the guidance of the idea of material genomics.Then,large-scale computational materials screening studies were carried out to examine the performance of these MOFs toward the applications of C2H4 purification and SF6 separation.The main research work is outlined as follows:1.Based on the results of Density Functional Theory(DFT)calculations,an accurate molecular force field was developed to describe the interaction between C2H4 and the open Cu sites in the Cu2(COO)4 unit,from which a large-scale computational screening was performed to study the separation behaviors of C2H2/C2H4 mixture in collected MOFs.According to the structure-activity relationships established from the simulation results,the structural features of optimal materials were proposed.Based on three high-performance materials identified,materials design was further carried out through introducing fluorine group(-F)into organic ligands in different degrees.The results showed that there is a significant synergistic effect between the unsaturated Cu sites and the F atom on the benzene rings near the copper site,which can greatly improve the performance of materials for C2H2 separation.2.Based on the force field developed previously,a computational materials screening for C2H4/C2H6 separation was carried out.According to the simulation results,optimal ranges of the structural features for high-performance materials were established,from which one promising MOF was identified.The important role of open metal sites in strengthening the separation process was also revealed through mechanism analysis.The modification effect of several groups on high-performance materials was evaluated,and it was found that parent material with hydroxyl group(-OH)significantly improved the separation performance of C2H4/C2H6.3.By comparing the results obtained from various potential models for SF6 molecule,this work selected the most accurate model with seven-charged-site model was selected to probe the separation performance of MOFs for SF6/N2 mixture.By disclosing the optimal structural features,five materials that could efficiently separate SF6/N2 were identified,whose separation performances exceed those reported in the literature at the moment.