Study On The Preparation Of Metal-Organic Frameworks(MOFs) And Their Performance Of Photocatalytic(Thermal) Catalytic Organic Transformations

Recently,metal-organic frameworks（MOFs）,a kind of novel porous materials,have attracted enormous interest on scientific researchers.They have been widely applied in fluorescence sensing,molecular medicine,drug delivery,molecular recognition,gas adsorption and separation,gas storage and catalysis by take the advantages of the diverse structures,high porosity and adjustable functions,as well as facile synthesis methods.In this paper,1,3,6,8-Tetra（4-carboxylphenyl）pyrene（TBAPy）and pyridine-functionalized boron dipyrromethene（BODIPY）,5-（pyridyl-4-methoxy）-isophthalic acid（5,4-PMIA）and biphenyl-3,4’,5-tricarboxylic acid（BPT）were employed as the organic linkers,combined with the different transition metal ions to construct 6 kinds of MOFs.In chapter 1,the related basic concept of MOFs were firstly introduced,then the research progress of MOFs in the field of photo（thermal）catalytic organic reactions and other related fields were presented successively.In chapter 2,three novel MOFs,[Co₂（BODIPY）（5,4-PMIA）₂]·（DMA）_1.5·（H₂O）₁₀（Compound 1）,[Ni（BODIP Y）（5,4-PMIA）]·（DMA）·（H₂0）₂（Compound 2）and[Ni（BODIPY）₂（BPT）₂（H₂O）]·（H₂O）（Compound 3）were constructed by employing BODIPY and 5,4-PMIA,BPT as the organic ligands,the transition metal ions(Co²⁺,Ni²⁺)as the metal center through solvothermal method.And the compound 1 was applied to photocatalytic oxidation of benzylamine.Firstly,the possible affect factors,such as reaction time,solvents and light source on the reaction were explored to determine the optimal catalytic conditions.The band gap of compound 1 was estimated to be 2.09 eV by a conversion from its UV-Vis spectrum.And the LUMO energy of compound 1 is-1.05 eV determined by Mott-Schottky（M-S）curve,which is more negative than the E(O₂/O₂^·-),thus it is possible for the electrons transfer to O₂ to generate O₂^·-.Then the EPR characterization results indicate the generation of 102 and O₂^·-during the reaction.Through literature research and quenching experiments,it is speculated that benzylamine can undergo auto-oxidation to produce a reaction intermediate(PhCH₂NH₂^·+),and then PhCH₂NH₂^·+ reacts with O₂^·-to form a highly active phenylmethanimine（PhCH=NH）,The coupled imine product was generated by the nucleophilic addition reaction between PhCH=NH and benzylamine.Another benzylamine oxide pathway:under light（6 W）irradiation,The catalyst passes through the inter-system energy transfer to O₂ to form reactive oxygen species ¹O₂,and ¹O₂ reacts with the substrate to produce to form a highly active phenylmethanimine（PhCH=NH）intermediate.The coupled imine product was generated by the nucleophilic addition reaction between PhCH=NH and benzylamine.For compound 2,it can be employed to catalyze nitrobenzene reduction.Firstly,through various control experiments,the influence of various possible factors such as temperature,solvent,time on the reaction were discussed,and finally confirmed the optimal catalytic conditions.According to the literatures,the possible mechanism of compound 2 can be inferred:the positively charged pyrrole ring of BODIPY in compound 2 binds to BH₄^-in NaBH₄ through electrostatic interaction,and then hydrogen atoms on BH₄^-gradually reduce the substrate to produce the target aniline,realizing the efficient reduction of nitrobenzene.In this chapter,by studying the influencing factors of various catalytic reactions in the photocatalytic benzylamine oxidation and nitrobenzene reduction reactions,the possible reaction mechanisms are proposed,which will provide a vital reference for the further research on this kind of reactions.In chapter 3,three kinds of MOFs,[Co₂（TBAPy）（H₂O）₂]（Compound 4）,[Ni₂（TBAPy）（H₂O）]（Compound 5）,and[Cu₂（TBAPy）（H₂O）₂]（Compound 6）were obtained by using 1,3,6,8-tetra（4-carboxybenzene）pyrene（TBAPy）as organic ligand,transition metal ions(Co²⁺,Ni²⁺,Cu²⁺)as metal center.Thereinto,the structures of compounds 4 and 6 are similar,and these three kinds of MOFs all possess Lewis-acidic sites（coordination unsaturated metal nodes）,making it possible to apply for the epoxidation of styrene.Firstly,the possible affect factors,such as reaction temperature,reaction time,solvents and the usage of catalysts on the reaction were explored to determine the optimal catalytic conditions.According to the literatures,it is proposed that the possible mechanism of compound 4,compound 5 and compound 6 catalyzing the styrene epoxidation reaction:the coordinated unsaturated metal node acts as a Lewis acidic site and forms a three-membered ring intermediate with O₂.At this time,The oxidation state of Co²⁺ in the metal center of compound 4 will change（+2 changes+3）,the three-membered ring intermediate further reacts with styrene to form a five-membered ring intermediate,and then the five-membered ring intermediate undergoes a ring-opening reaction to produce styrene and benzaldehyde,and at the same time the metal center Co³⁺in compound 4 is restored to Co²⁺,compound 4 is restored to its original state,and the next cycle of catalysis begins.Compared with Cu²⁺ and Ni²⁺,Co²⁺ is easier to achieve the transition between oxidation states,making compound 4 easier to form intermediates in the catalytic reaction,which may be the reason why compound 4 exhibits better catalytic performance in catalyzing styrene epoxidation.This chapter focuses on the factors that may affect the catalytic performance of the three compounds in the styrene epoxidation reaction,and the possible reaction mechanism of the reaction was proposed.It is of great significance for catalytic olefin epoxidation by using MOFs as catalysts.And it will also provide an important reference for the further development of olefins epoxidation.In chapter 4,the summary of the research results and innovations,as well as the potential prospects of MOFs in light（thermal）catalyzed organic reactions have been proposed.