Synthesis And Catalytic Study Of Sulfo And Sulfometal Functionalized Porous Crystalline Materials

Metal organic frameworks?MOFs?and covalent organic frameworks?COFs?are both promising crystalline materials.MOFs are formed by coordination of metal or metal clusters and organic ligands,and COFs are formed by only organic linkers.Both of them are crystalline materials.The atoms,ions,molecules or clusters in crystalline materials have periodic regular arrangement and are easier to be analyzed and characterized due to their regular structure.In addition,the two materials have similar advantages of large specific surface area,easy modification,adjustable poresize,high thermal stability and chemical stability,and can be used as catalysts for a variety of reactions.In this thesis,several MOF and COF materials with sulfonic acid group were designed and synthesized,and their performance in catalyzing A³reaction?alkyne-aldehyde-amine reaction?and cyclohexene oxidation were tested.After condition optimization,high conversion and reaction rate could be obtained.In addition,the thesis clarified the mechanism of catalytic reactions,which would be significant for further research on catalysis using sulfo and metal functionalized porous crystalline materials.The content of this thesis includes the following three parts:1.Studies on A³ reactions catalyzed by MIL-101-SO₃Cu and MIL-101-SO₃AgMIL-101,consisting of Cr clusters and terephalate linkers,is remarkable for its high specific surface area,excellent thermal stability and acid stability.In this thesis,two sulfometal-functionalized MIL-101-type MOFs were prepared and successfully applied to catalyze the alkyne-aldehyde-amine?A³?coupling reaction,which is an important synthetic approach to propargylamines.?1?MIL-101-SO₃Ag and MIL-101-SO₃Cu catalysts were synthesized and characterized.The specific surface area,functional groups,metal loading,etc.were confirmed,and the structure of MOFs proved to be maintained after metal modification.?2?MIL-101-SO₃Ag and MIL-101-SO₃Cu were used as catalysts for the A³model reaction of phenylacetylene,paraformaldehyde and piperidine.By changing the solvent,the catalyst loading and the reaction temperature,the reaction conditions were optimized.Both MIL-101-SO₃Ag and MIL-101-SO₃Cu could complete A³model reaction in very short time and require little catalyst loading.In comparison,MIL-101-SO₃Cu has better performance.Under 10 ppm?calculated by Cu?catalyst amount,the conversion of alkyne reaches 57%within 5 minutes,and the turnover frequencies is up to 6.8×10⁵ h^-1.The two catalysts are also effective in other A³reactions with aliphatic aldehyde assubstrate.?3?In the A³ reactions with an aromatic aldehyde as substrate,both catalysts produced chalcone after a period of time.The formation of chalcone involves the metal and base?piperidine?catalyzed isomerization from propargyl to allenyl,followed by hydrolysis of allenylamine.The cause of this reaction is the acidity of?–hydrogen of the aryl propargylamine,and aliphatic aldehydes can not undergo similar reactions because the acidity of the propargyl imtermediate is not strong enough.?4?The domino reaction combining A³ coupling and 5-endo-dig cyclization was successfully catalyzed by MIL-101-SO₃Cu.Indole rings can be formed by this one-pot reaction.Under the same conditions as A³ coupling,the p-amino-substituted aromatic aldehyde undergoes not only the target domino reaction but alos intramolecular cyclization.After condition optimization,the target product can be obtained in high yield.In addition,indole products with different groups can be achieved by changing substrates.2.Studies on cyclohexene oxidation catalyzed by MIL-101-SO₃HCyclohexene oxidation is a typical olefin oxidation.Both double bond and?-hydrogen of cyclohexene can be oxidized.Through this reaction,2-cyclohexen-1-one?1-one?,2-cyclohexen-1-ol?1-ol?,cyclohexene epoxide?epox?,1,2-cyclohexanediol?diol?and other products can be obtained.These compounds are widely used in organic synthesis,pharmaceutical chemistry,polymer synthesis,etc.As a bifunctional catalyst with Lewis acid and Br?nsted acid,MIL-101-SO₃H is of great significance to explore the influence of different catalytic sites on reaction.In this chapter,MIL-101-SO₃H was applied to the catalytic oxidation of cyclohexene,and a series of control experiments were carried out to investigate the role of different catalyst sites in reaction.?1?Products at different time were analyzed by GC-MASS to fully understand the process of cyclohexene oxidation catalyzed by MOF.The data confirmed that the oxidation of cyclohexene proceeds through two routes:route A,oxidized at?-hydrogen,through 3-hydroperoxycyclohex-1-ene?perox?to 2-cyclohexen-1-one?1-one?and then to 2-cyclohexen-1,4-dione?dione?;route B,oxidized at double bond,through cyclohexene epoxide?epox?to 1,2-cyclohexanediol?diol?.Rarely reported dione product can be easily obtained in this system,while the frequently reported2-cyclohexen-1-ol product did not appear.?2?By changing a series of conditions such as the solvent,the oxidant dose,the catalyst amount,the reaction temperature and the reaction atmosphere,the product distribution under different conditions was tested.Increasing the catalyst loading,the oxidant dose or the temperature can accelerate the oxidation process,and increasing catalyst loading and temperature will increase the yield of the route B products.O₂facilitates the production of dione and diol,but it cannot oxidize cyclohexene alone.It serves as co-oxidant in cooperation with TBHP.The radical inhibitor test indicated that all the reactions except the decomposition of perox in cyclohexene oxidation are radical-involving processes.?3?By comparising MIL-101-SO₃H with p-toluene sulfonic acid,MIL-101 and MIL-101-SO₃Na,it proved that the reaction was catalyzed by both Cr cluster and sulfonic acid group,and there was a synergistic effect between the two sites.Cr cluster plays a major catalytic role in the generation of TBHP free radicals and the route A oxidation,while sulfonic acid group can improve the oxidation rate of route B and all oxygen-containing compounds.Based on the result,the oxidation processes of cyclohexene over MIL-101-SO₃H was proposed.3.Synthesis and A³ coupling catalytic study of covalent metal framework?COF?materials TpPa-SO₃Cu and TpPa-SO₃AgCOFs are also promisingcrystalline porous materials in recent years.In this part,an imine-based COF,TpPa-SO₃H was synthesized and Cu and Ag were loaded on the material.The catalytic performance of two materials was tested,and the result wascompared with systems of MIL-101-SO₃Cu and MIL-101-SO₃Ag.After characterization,we confirmed that the catalysts were amorphous covalent polymer but not COFs.Catalytic experiments showed that the two materials can efficiently catalyze the A³ model reaction of phenylacetylene,paraformaldehyde and piperidine,and the activity of two materials is between that of MIL-101-SO₃Ag and MIL-101-SO₃Cu.The two covalent polymer catalysts are recyclable.Experiments of different substrates showed chalcone products also appeared when aromatic aldehyde used as substrate,and this process could be inhibited by strong electron substituent.The synthesis of crystal type metal-loaded COF catalyst needs to be further studied.