Synthesis And Modification Of Zr-MOF And Their Catalytic Oxidation Application

After nearly 30 years of rapid development,metal-organic frameworks（MOFs）have shown attractive attention in catalysis.They have been proved to be one of the most promising porous materials as catalyst or as catalyst supports for their regular structure,large specific surface area and tunable structure.Among the reported MOFs,Zr-based UiO-67（BPY）plays an important role in the field of heterogeneous catalysis,for the N-heterocyclic ligand,2,2’-bipyridine-5,5’-dicarboxylic acid（H₂BPYDC）,endowing the material flexibility in design and modification.In this thesis,a series of metal peroxide complex modified Zr-based UiO-67（BPY）MOFs were prepared via post-synthetic modification（PSM）method and pre-synthetic modification method.The uniform distribution of bipyridine chelating sites on the frameworks enables catalytic active species to work as homogeneous catalytic sites in the reaction system.The obtained catalytic materials have been applied to liquid phase oxidation reactions.UiO-67-MoO（O₂）₂,UiO-67-WO（O₂）₂ and UiO-67-KVO（O₂）₂ catalysts were successfully prepared by anchoring a series of metal peroxides（MoO（O₂）₂,WO（O₂）₂ and KVO（O₂）₂）on bipyridine coordination sites in UiO-67（BPY）by PSM and pre-modification.The physiochemical properties of the resulting catalysts were characterized using FT-IR,FT-FIR,XRD,XPS,SEM,HRTEM and N₂ adsorption/desorption techniques.The three resulting catalysts were used to catalyze oxidative desulfurization（ODS）with cumene hydroperoxide（CHP）as the oxidant,and their catalytic activity in the oxidation of sulfur compounds were investigated.The performance of UiO-67-WO（O₂）₂ and UiO-67-KVO（O₂）₂ in the oxidation of benzothiophene（BT）,dibenzothiophene（DBT）and4,6-dimethyldibenzolthiophene（4,6-DMDBT）at 20-40℃was investigated.Also,the stability of UiO-67-KVO（O₂）₂ and the effect of by-product（dimethylbenzyl alcohol）on the catalytic activity were investigated.The results showed that the DBT conversion for UiO-67-KVO（O₂）₂ catalysts retained above 90%throughout the 140 h test and the framework of UiO-67-KVO（O₂）₂ is well preserved after the long-time catalytic ODS reaction with no significant leaching of metals species.In addition,dimethyl-benzyl carbinol can obviously hinder the DBT conversion.The three resulting catalysts were used to catalyze the epoxidation of propylene with CHP as the oxidant,and their performance was investigated.The activity of the three catalysts is quite different,UiO-67-MoO（O₂）₂ shows the best catalytic activity among them all.The effects of reaction temperature,solvent and reaction time on the catalytic performance with UiO-67-MoO（O₂）₂ as catalyst were investigated.The results showed that the yield of propylene oxide(Y_PO)was higher when the solvent has lower polarity.The epoxidation activity of propylene is obviously affected by reaction temperature and reaction time.In a 9 h reaction at 80℃,0.6 MPa propylene pressure,the CHP efficiency(E_CHP)is 56.0%and the Y_PO is 38.5%with dichloromethane as the solvent.The UiO-67-MoO（O₂）₂ framework remained the structure integrity after reaction.