The Synthesis Of Several Metal-Organic Frameworks And Their Adsorption Performances Of CO₂ Capture And Olefin/Paraffin Separations

The efficient CO₂ capture as well as high-efficiency and energy-saving olefin/paraffin(C₂H₆/C₂H₄ and C₃H₆/C₃H₈)separations are highly important for chemical industries,and also are hot topics in the field of science and technology in chemical separations to date.In this thesis,several metal-organic frameworks(MOFs)have been designed and investigated in their adsorption and separation performances for CO₂ capture from flue gas and natural gas,olefin/paraffin separations.This work mainly involves the synthesis and characterizations of several MOFs,CO₂/N₂,CO₂/CH₄,C₂H₄/C₂H₆ and C₃H₆/C₃H₈ adsorption and separation performances and mechanisms.It belongs to the interdisciplinary fields of chemical engineering and material science,which is of great importance for scientific research and practical applications.In this thesis,we reported a new MOF-505@GO composite with high selectivities for CO₂/CH₄ and CO₂/N₂ separation.The copper-based MOF-505 and graphite oxide(GO)were selected for the synthesis of moisture stable MOF-505@GO composite.At 298 K and 100k Pa,MOF-505@5GO exhibited the CO₂ uptake of 3.94 mmol/g and the CO₂/CH₄ and CO₂/N₂selectivities of MOF-505@5GO were calculated up to 8.6 and 37.2,respectively.Compared with the parent MOF,the CO₂ uptake of of MOF-505@5GO had an increase of 37.3%and the CO₂/CH₄ and CO₂/N₂ selectivities of MOF-505@5GO separately increased by13.2%and33.8%.It provided an efficient method for improving CO₂ adsorptive separation performance through utilizing the enhanced dispersive force and steric effect by incorporating MOFs with GO.In this thesis,we reported an unusual moisture-enhanced CO₂ capture within microporous PCN-250 frameworks.Compared with the parent PCN-250(Fe₃),PCN-250(Fe₂Co)showed an improved CO₂ adsorption performance due to the partial Co²⁺ions substitution in PCN-250 framework.The two materials showed an unusual moisture-enhanced adsorption of CO₂ by converting the negative competitive coadsorption of water into the positive effect on CO₂ adsorption.Under 50%RH humid condition,the CO₂adsorption capacities of PCN-250(Fe₃)and PCN-250(Fe₂Co)increased by 54.2%and 68.9%compared to dry condition,respectively;even up to 90%RH,obvious increases of 43.7 and70.2%in the CO₂ adsorption capacities were also observed.Molecular simulations indicated that the hydroxo functional groups(?₃-O)within the framework played a crucial role in improving CO₂ uptake in the presence of water vapor,which is the novelty of this work.In this thesis,we reported an C₂H₆-trapping MOF PCN-250 for highly selective adsorption of C₂H₆ over C₂H₄.At 298 K and 100 k Pa,adsorption capacities of C₂H₆ and C₂H₄were 5.21 and 4.22 mmol/g,respectively;the adsorption selectivities of C₂H₆/C₂H₄ mixtures(1:15 and 1:1,v/v)were 1.9.Meanwhile,its separation performance was also corroborated by the breakthrough experiments,indicating the potential of C₂H₄ purification from C₂H₆/C₂H₄mixtures.Computational simulation revealed that both the pore effect and the van der Waals adsorption energy governed the separation of C₂H₆ over C₂H₄ for PCN-250,especially at low pressures.It can provide some useful theory for designing C₂H₆-selective MOFs.In this thesis,we reported an efficient adsorptive separation of C₃H₆ over C₃H₈ on a flexible and thermoresponsive CPL-1.It can achieve the adsorptive separation of C₃H₆ over C₃H₈ via the gate opening adsorption for C₃H₆ whereas not for C₃H₈ on the flexible CPL-1 at273 K.Since CPL-1 had only surface adsorption for both C₃H₆ and C₃H₈ at 298 K and up to100 k Pa.Thus,we developed an efficient regeneration of CPL-1 at 298 K based on its thermoresponsive gate opening effect.Molecular dynamics simulation revealed that the hydrogen bonding was a key factor governing the selective adsorption of C₃H₆ over C₃H₈ in CPL-1.It was because C₃H₆ molecules could be more preferentially adsorbed to form hydrogen bonds due to the slight rotation of the pyrazine ligand and then its structural transformation triggered the consequence of opening the pores.In this thesis,we reported a pillar-layer metal-organic framework for efficient adsorption separation of C₃H₆ over C₃H₈.There is an unsaturated metal site within the Zn(II)center for[Zn₂(5-aip)₂(bpy)]·(DMF)·(H₂O)₂(Zn-aip-bpy)framework,which can selectively form specific interaction between the?-orbital of C₃H₆ molecule and the vacant s-orbital of unsaturated Zn(II)atom.Although Zn-aip-bpy had C₃H₆ adsorption capacity of 1.91 mmol/g at 100 k Pa and 298 K,it exhibited preferential adsorption of C₃H₆ over C₃H₈ with high C₃H₆/C₃H₈ adsorption selectivity up to 19.8,outperforming most widely investigated MOFs.Furthermore,breakthrough experiments demonstrated the efficient separation of C₃H₆ over C₃H₈ on Zn-aip-bpy.This material could be readily regenerated at 423 K within 20 min.