Application And Mechanism Of Modified GO Materials In Adsorption And Separation Of CO₂

Due to the increasing use of fossil energy and the expanding scope of human activities,carbon emissions have caused the greenhouse effect of severe ecological and environmental consequences.How to effectively reduce the concentration of carbon dioxide(CO2)in the atmosphere,how to separate CO2 from mixed gases,and how to adsorb and reuse CO2 are the urgent scientific and engineering problems of humankind.In my master’s thesis,I focused on the research of CO2 adsorption and separation by graphene oxide(GO)and its composites.My research consists of two parts:(1)Exploring the optimal layer spacing of CO2 adsorption in diamine-intercalated GO materials.I used different alkyl diamine molecules to intercalate the layers of GO and systematically expanded its interlayer spacing from 0.762 nm to over 1.030 nm.Their subtle chemical or compositional differences were characterized by Fourier Transform Infrared Spectroscopy(FT-IR),X-ray Photoelectron Spectroscopy(XPS),Elemental Analyzer(EA),X-ray Diffraction(XRD),Solid State Nuclear Magnetic Resonance(SSNMR)methods.We found that CO2 uptake maximized at the interlayer spacing of 0.860 nm.I used in situ 13C NMR at variable temperatures to investigate the dynamics of CO2,and it revealed both physically and chemically adsorbed CO2.In particular,we observed the unique state of CO2 which are physically trapped in GO layers of 0.860 nm spacing by Van der Waals interactions.This state of CO2 was not observed in GOs with either smaller or larger interlayer spacings.Our study not only demonstrated the "optimal spacing" effect but also revealed the molecular mechanisms for CO2 adsorption.(2)A high-throughput and high-selective carbon dioxide separation membrane of ionic liquid/graphene oxide membrane was prepared,and its gas separation mechanism has been studied.The layered anions facilitate CO2 transportation with a permeance of 68.5 GPU.The C02/H2,C02/CH4,and CO2/N2 selectivities are 24,234,and 382,respectively,which are up to 7 times higher than that of pristine GO membranes.FT-IR,SEM,XRD,and SSNMR have been used to characterize the morphology and structural changes of materials.I analyzed the distribution of the ionic liquid in GO film by 1H-13C HETCOR experiment.Our experimental results were coupled with computer simulation to uncover the transfer trajectory of CO2.We found the interaction between the CO2 and[BF4]-forms a fast lane for transporting CO2 molecules within the GO-SILM membrane.