Synthesis Of Benzothiadiazole Functionalized Porous Materials And Visible-light Driven Oxidation Of Sulfides

2,1,3-benzothiadiazole（BT）is a strong electron-withdrawing group,which has been widely used as photoactive building blocks for the construction of photoactive materials due to its strong electron affinity,high oxidation potential,excellent stability,easy functionality,and wide absorption spectrum in the visible light region.In this thesis,we focused on the synthesis of benzothiadiazole functionalized conjugated microporous materials（CMPs）and metal-organic frameworks（MOFs）.The structure and morphology of BT functionalized CMPs and MOFs can be controlled by the size and geometry of aromatic alkynes,as well as the types of modulators,and their catalytic activity toward the visible-light driven oxidation of sulfides was invesitigated.Finally,three benzothiadiazole molecules bearing different end-groups were synthesized,which can be used for the construction of new photoactive porous materials.The main research contents are following:1.By using 4,7-dibromo-2,1,3-benzothiadiazole as a photoactive building block,the Sonogashira coupling between4,7-dibromo-2,1,3-benzothiadiazole and 1,3,5-triethynylbenzene,1,3,6,8-tetramethylpyrene,tetrakis（4-ethynylphenyl）ethene,tetrakis（4-ethynylphenyl）methane,results in the formation of benzothiadiazole functionalized conjugated microporous polymer（CMPs）,named CMP-3-BT,CMP-Pyrene-BT,CMP-Alkene-BT,PAF-4-BT.Scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,Fourier infrared spectroscopy（FT-IR）,X-ray diffraction（XRD）,UV-Vis diffuse reflectance spectroscopy（UV-Vis DRS）,element-analysis（CHN）,solid state EPR and solid state NMR were used to investigate the composition,morphology and structural characteristics of CMP-3-BT,CMP-Alkene-BT,CMP-Pyrene-BT and PAF-4-BT.The catalytic activities of the above catalysts were studied by the conversion of phenyl sulfoxide to methyl phenyl sulfoxide under visible light irradication.Our results indicated that by using LED（425 nm,3W）as a light source,assisted by H₂O₂,CMP-3-BT enables the oxidation of thioanisole bearing various substituents to their corresponding sulfoxides under O₂ atmospheres at room temperature with high efficiency and excellent selectivity.Importantly,the catalytic activity of CMP-3-BT remained unchanged after 6 cycles.Under otherwise identical conditions,PAF-4-BT and CMP-Alkene-BT show better catalytic activities that than CMP-3-BT,and more importantly,no H₂O₂ is needed in the reaction system.However,CMP-Pyrene-BT showed worse catalytic activity toward the oxidation of sulfides.The reason might be the p-p stacking of pyrene molecules,which against the efficient separation of photo-induced eletron/hole pairs.The EPR experiments indicate that the ¹O₂ and O₂^·-are the active oxygen species for the photo-oxidation of thioanisole.2.The incorporation of benzothiadiazole into 4,4’-triphenyl dicarboxylic acid results in 4,4’-[2,1,3-benzothiadiazole-4,7-diyl] dibenzoic acid（H₂tpdc-BT）.The solvothermal reaction between H₂tpdc-BT and Zr（IV）salt,accompied withacetic acid,benzoic acid,trifluoroacetic acid,hydrochloric acid and L-proline as tmodulators,results in benzothiadiazole functionalized Zr-MOF-BT nanosheets.The effects of different templating agents and concentrations on the morphology and structural characteristics of Zr-MOF-BT were investigated by SEM,TEM,XRD,FT-IR and UV-Vis diffuse reflectance spectroscopy.When the concentration of acetic acid was 0 eq,5 eq,30 eq,60 eq,the morphology of Zr-MOF-BT gradually changed from shells to sheets with increased crystallinity.The Zr-MOF-BT obtained by using benzoic acid,hydrochloric acid and proline as modulators results in irregular nanoplates,while the agglomerated irregular nanoblocks were obtained when trifluoroacetic acid used as a modulator.By using LED（425 nm,3W）as a light source,The Zr-MOF-BT_{（30 eq HOAc）}show the highest photocatalytic activity toward the oxidation of sulfides under O₂atmospheres at room temperature.Zr-MOF-BT_{（30 eq HOAc）}enables the oxidation of thioanisole bearing various substituents to their corresponding sulfoxides with high efficiency and excellent selectivity.Importantly,the catalytic activity of Zr-MOF-BT_{（30 eq HOAc）}remained unchanged after many cycles under CH₃CN or H₂O;Zr-MOF-BT_{（30 eq TFA）}also enables the oxidation of thioanisole bearing various substituents to their corresponding sulfoxides under O₂ atmospheres at room temperature with high efficiency and excellent selectivity.However,the resusibility of Zr-MOF-BT_{（30 eq TFA）}is worse than that of Zr-MOF-BT_{（30 eq HOAc）}.The EPR experiments indicate that the ¹O₂ and O₂^·-are the active oxygen species for the photo-oxidation of thioanisole.3.By using 4,7-dibromo-2,1,3-benzothiadiazole as a starting material,a series of benzothiadiazole molecules bearing different end-groups,named4,7-bis（B₂Pin₂）-[2,1,3]-benzothiadiazole,4,7-bis（4-aminophenyl）-[2,1,3]-benzothiadiazole,and 4,7-diethynyl-[2,1,3]-benzothiadiazole were synthesized and characterized by FT-IR,NMR,and HRMS.These molecular building blocks can be used for the construction of new photoactive porous materials.