Preparation And Gas Separation Performance Of Zirconium Metal-organic Framework Composite Membrane

Membrane separation technology plays an important role in carbon capture technology because of its low energy consumption and cost.Compared with organic polymeric membranes and inorganic zeolite membranes,MOF membrane has plenty of diverse types,adjustable pore structure,pore size,and function,so it has natural advantages in gas separation.The zirconium-based organic framework has been widely used in the field of membrane separation due to its strong adsorbability and high stability.However,the current synthesized Ui O-66 membranes have poor adhesion to the substrate,which is easy to fall off.In this thesis,a novel coupling method was used to graft-COOH onto a ceramic substrate surface,thereby providing more nucleation sites and enhancing the adhesion of the membrane to the substrate.The origins of surface defects of the Ui O-66 membrane were analyzed,and the recovery of defects by polymer was studied.Finally,we prepared a mixed matrix membrane with Ui O-66-NH₂ as the dispersing phase and studied its gas separation performance.Specific work is as follows:（1）We used an alumina ceramic membrane as the substrate.Under the action of coupling agent KH560,2-amino-terephthalic acid（BDC-NH₂）was grafted to the substrate,and the Ui O-66 membrane was prepared by in situ seeding and secondary crystallization method.The influences of KH560 hydrolysis time,crystal growth time,regulator content,temperature,and zirconium source on the adhesion and morphology of the membrane were investigated.It was found that the coupling agent had a significant effect on the adhesion between the Ui O-66 membrane and substrate.After24 h coupling reaction at room temperature and secondary growth using Zr S₂ as zirconium source,a UiO-66 membrane with flat and compact surface and strong adhesion to substrate was obtained.（2）The UiO-66 membrane prepared above was applied to the separation of CO₂/N₂,and its CO₂ permeance reached 8726 GPU.Because of the tiny cracks in the membrane,the membrane has no separation selectivity in the gas separation performance test.The cracks were recovered by applying Pebax on the surface of the membrane by drip coating.When the concentration of Pebax is 0.5%,the ideal selectivity of CO₂/N₂ is 30.15 and the permeance of CO₂ is 30.45 GPU.This recovery strategy provides a useful reference for the recovery of metal-organic framework membrane defects.（3）The UiO-66-NH₂ nanoparticles were synthesized by ZrCl₄ and 2-amino-terephthalic acid and then added into polyimide（PI）matrix containing-COOH to prepare mixed matrix membrane（MMM）.The effects of different MOF additions on gas separation performance were studied.The permeability of CO₂ increased from60.15 to 93.46 Barrer and the selectivity of CO₂/N₂ is 30.74 when the addition of Ui O-66-NH₂ is 1%.FT-IR and SEM characterization implies that the MMM’good gas selectivity is due to the interaction between-NH₂ in MOF structure and-COOH in PI structure,which enhances the interfacial compatibility.This method provides a new strategy for enhancing the interface compatibility of MMM.