Study On The Construction And Application Of Stable UiO Series Metal-Organic Frameworks Based On Click-Chemical Reaction

Metal-organic framework(MOFs)materials have been considered to be the most important kind of porous materials due to their unique properties and wide application.However,due to the weak coordination bonds of MOFs,a large number of MOFs have the disadvantage of poor stability in water,acid,base and salt solutions,which will limit their practical application.To solve the stability problem of Ui O series MOFs,through the method of postsynthetic modification(PSM)in this paper,the hydrophobic molecular layer was constructed on the surface of MOFs based on thiol-ene click chemistry and combined with embedded polymer to improve the stability of Ui O-66 and Ui O-67.The obtained stable MOFs were used for oil-water separation and CO₂ adsorption.The main research of this paper is as follows:(1)Using a simple,environment-friendly,and mild reaction conditions postsynthetic modification(PSM),1H,1H,2H-perfluoro-1-hexene or 1H,1H,2H-perfluoro-1-decene low surface energy molecules were introduced into organic ligand through thiol-ene click reaction on sulfhydryl group of superhydrophilic Zr(Hf)-Ui O-66 to make MOFs superhydrophobic.The water contact angles of the modified Ui O-66 MOFs were all greater than 150^o.The grafted low surface energy fluorine-containing molecular chains acted as an effective protective layer for MOFs,making them remarkably stable under extreme conditions such as alkaline(p H=12),concentrated HCl solution and high concentration Na Cl solution(20 wt%).The CO₂ adsorption capacity of Zr-Ui O-66 MOFs grafted with 1H,1H,2H-perfluoro-1-hexene reached 1.54 and 2.88 mmol·g^-1 at 298 K and 273 K.In addition,superhydrophobic MOFs also showed good oil-water separation performance.(2)Using the"internal and external binding"strategy,polyethyleneimine(PEI)with imine group was first cross-linked with pentarythritol tetra-3-mercaptopropionate(PTMP)crosslinking agent with mercapto group and ester group,and the functional crosslinking network with mercapto group was obtained.Then,the crosslinked network was wrapped on the outer surface of Ui O-67 to obtain the mercaptohydrated Ui O-67-SH.The1H,1H,2H-perfluoro-1-hexene and 1H,1H,2H-perfluoro-1-decene were introduced through thiol-ene click chemistry to give Ui O-67-SH@F₆ and Ui O-67-SH@F₁₀.Contact angle test showed that Ui O-67-SH@F₆ and Ui O-67-SH@F₁₀ have superhydrophobic and superoleophobic properties.Compared with Ui O-67,the stability of Ui O-67-SH@F₆ in water,acid,alkali and salt solutions could be effectively improved.In addition,in order to improve its mechanical stability,polymer polyethylenimine(PEI),polyvinylpyrrolidone(PVP)and polydopamine(PDA)were effectively embedded into Ui O-67 to obtain Ui O-67-PEI,Ui O-67-PVP and Ui O-67-PDA samples.PXRD showed that the crystalline structure of Ui O-67 embedded polymer by vacuum drying after water immersion was well preserved.Finally,the superdiphobic samples could be used for efficient separation of oil-water mixtures,incompatible organic liquids and water-in-oil emulsions.