Synthesis Of Supported Organic Electrocatalysts And Their Selective Electro-oxidation Of C-H Bonds And Alcohols

Aromatic aldehyde is a kind of important organic intermediates and fine chemical products,it is widely used in chemical,pharmaceutical,spice,food and other industries.There are many methods for the synthesis of aromatic aldehydes.However,researchers have to study new synthetic methods because of the high energy consumption and environmental pollution of the traditional chemical synthetic methods.Organic electrochemical synthesis has become a research hotspot as a green and environmentally friendly synthesis method.The electro-catalytic oxidation is an important means of organic electro-chemical synthesis.While it is easily led to passivation of the electrode and degradation of current efficiency in the direct electro-oxidation because of the polymer produced on the surface of the electrode.The indirect electro-oxidation with mediators can effectively avoid the problems,and the further oxidation of the product could be prevented.In indirect electro-oxidation,the applicable range of metal mediator is narrow because of the unadjustability of the redox potential,while the redox potential of the organic mediator could be adjusted by inducing different substituent groups.But it is difficult to be recycled because of the small dose of the organic mediator in the reaction.In this thesis the immobilization of the organic mediators for easily reuse will be studied,and the catalytic oxidation performance was improved because of the synergy of organic mediator and supporting material.The triphenylamine(P)and carbazole(C)mediator were synthesized and characterized by ~1HNMR.The immobilized organic mediators,marked as SP and SC,respectively,were prepared through chemically fixing onto multi-walled carbon nanotubes(MWCNTs),and characterized by fourier transform infrared(FTIR)spectrometry and thermogravimetry analysis(TGA).The catalytic performance of supported organic electro-catalysts were studied by cyclic voltammetry(CV)and potentiostatic electrolysis.SP and SC showed excellent electro-catalytic performance on benzyl alcohols with different para-substituent.The yields and selectivities of the corresponding aldehydes produced were high than 98%,except the yield of p-nitrobenzaldehyde was 88%.All the electrolysis were carried out at potentials lower than that of the substrates.The addition of water has little effect on the electro-catalytic oxidation of benzyl alcohols under SP and SC.The electrolysis potential of benzyl alcohol with electron-donating groups under SC was lower than that of SP.When the C-H bond of different toluenes is oxidized,SP and SC showed good catalytic activity on the elecro-oxidation of toluene derivatives with electron-donating group.Compared the activities of SP and SC,SC is suitable for the electro-oxidation of substrates with higher oxidation potential,while SP is suitable for the electro-oxidation of substrates with low oxidation potential.The addition of water has a great influence on the electrolysis results.Under 10mg SP,the yield of p-methoxybenzaldehyde for the electro-oxidation of p-methoxytoluene was 58%at 1.2V without water,while the yield reached to 91%when 15%(volume fraction)of water was added.The immobilized electro-catalysts SP and SC could be recovered and reused through simple filtration,and the electro-catalytic activity was maintained.