Understanding The Adsorption And Separation Behavior Of Sulfide In Metal-Organic Frameworks From Molecular Simulations

The content of SO₂,H₂S and other sulfide compounds in the air increase quickly with the consumption of coal,oil,natural gas and other fossil fuel,which results in pollution of environment and damage of human health,the natural gas pipeline equipment would also be corroded by the sulfide compounds.Therefore,it is of great significance to screen the microporous materials with high efficiently and ability of capture and separate sulfide compounds.Metal Organic Frameworks?MOFs?have been considered as the most promising material for the adsorption and separation of sulfide owing to the advantages of the high specific surface area and porosity,adjustable pore size,as well as good thermodynamics and chemical stability.The adsorption and separation behavior of sulfide could be investigated through adsorption and breakthrough experiments.However,there are so many MOF materials which have been reported and synthesized,if the methods discussed above are adopted to evaluate the adsorption and separation ability of these MOFs,the cost would be high,and the efficiency would be low.In recent years,molecular simulation methods have been employed to screen a large number of MOFs rapidly,the relationship between the structure of MOFs and the adsorption and separation properties could be revealed from molecular level.It also presents a supplement to traditional experimental methods and help us to understand the adsorption mechanism from molecular level.Unfortunately,the relationship between the adsorption and separation propertiesof sulfide in different MOF materials and their structural information is still unclear,In this thesis,Grand canonical Monte Carlo method?GCMC?was employed to investigate the adsorption and separation behavior of SO₂ in flue gas and H₂S in natural gas in different MOFs and the interaction mechanism between MOFs and sulfide was also discussed.The effect of topology,metal ions and organic linkers on adsorption and separation properties of the sulfide would be also revealed.The major contributions of this work are as follows:?1?The different topological structure results in different pore sizes distribution of ZIFs.At low pressure,the smaller pore size,the stronger interaction between sulfide and the frameworks of ZIFs,the adsorption amount of sulfide in ZIF-2 is highest due to its relative small pore.When move to the high pressure,the adsorption amount of sulfide in ZIFs increases with the increaseof the pore size or the surface area.Compared with other ZIFs,ZIF-3 shows better capture and selectivity for SO₂ in flue gas and H₂S in natural gas.?2?As to the materials of M-DOBDCs,when the angle formed between the organic linkers and unsaturated metal atoms is larger,the contact probability between SO₂ in flue gas and unsaturated metal site would be larger due to the configuration of SO₂,which results in the relative strong interaction between SO₂ and the frameworks of M-DOBDCs.On the contrary,the interaction between CO2 and the frameworks of M-DOBDCs with larger angle would be weak.This is good for separating SO₂ from flue gas.Zn-DOBDC shows the best capture and selectivity for SO₂ in flue gas due to the relative larger angle.When we move to the adsorption and separation processof H₂S in natural gas,it is in an inverse proportion to the capture and separation properties of M-DOBDCs and the angle formed between the organic linkers and unsaturated metal sites.It is found that the Mg-DOBDC material with the smallest angle is the best one for the capture and separation of H₂S from natrual gas.?3?For the UMCMs series materials with different organic linker,the positions of the N atoms in organic linker is different,which leads to the different charge density distribution in their pores.The sulfide inclined to be adsorbed most in the material of UMCM-150?N?1 since the nitrogen atom in its organic linker face to the main pore.The material of UMCM-150?N?1 has a good performance of capture and separation of SO₂ in flue gas and H₂S in natural gas.The capture ability and separation performance for sulfide would be improved when some polar functional groups are introduced to UMCM-150?N?1.When carboxyl and nitro groups are introduced to UMCM-150?N?1,they show high capture and separation ability for SO₂ from flue gas.As to the capture and separation of H₂S in natural gas.UMCM-150?N?1 modified by amino and carboxyl groups show better performance.