Transition Metal Catalysts Used In Electrocatalysisi C-H/P-O Oxidation Coupling To Produce Hydrogen

Organic synthesis can transform all kinds of small organic molecules into high value-added chemicals with various characteristics,which plays an important role in the development of human society.In organic synthesis,C-H/P-O functionalization is an important means to construct functional molecules.It is undoubtedly an ideal reaction mode to directly realize C-H/P-O functionalization coupling to produce hydrogen.In recent years,organic electrochemical synthesis has developed rapidly,which can realize the activation of substrate molecules through electrons,providing a green way for the construction of high value-added organic chemicals.However,there are still some problems in electrocatalytic C-H/P-O functionalization,such as low reaction yields and difficult separation and recovery of catalysts.In view of the above scientific problems,this thesis mainly focuses on the electrocatalytic anodizing to produce high value-added organic chemicals,and develops two clean and efficient electrocatalytic oxidation methods.Organic electrocatalytic synthesis can not only replace the oxidizing reducing agents with electricity,but also produce clean energy-hydrogen at the cathode.The synthesis of tetrahydroquinolines and organic phosphine oxides was achieved by electrocatalytic C-H/P-O bond oxidation.In addition,a variety of characterization methods have been used to reveal the reaction mechanism of electrocatalytic C-H bond activation.The main research contents and conclusions of this paper are as follows:（1）Cobalt-based catalyst（CCHH-A/CC）was constructed on the surface of carbon cloth by hydrothermal method and cyclic voltammetry.Then N,N-dimethyl p-toluidine and N-phenyl maleimide were used as reaction substrates to screen and optimize the electrode material,solvent,supporting electrolyte,current and voltage,and the optimal reaction conditions were determined as follows:Using CCHH-A/CC and Pt plate as anode and cathode respectively,tetrabutyl ammonium perchlorate as electrolyte,in Me CN/H₂O（1:1）mixed solvent at 3.0 m A for 12 h,tetrahydroquinoline compound was obtained at 86%yield.The universality of the substrate and experimental scale-up were subsequently verified.The reaction mechanism was further revealed by control experiments,free radical capture experiments,multi-potential step experiments,gas chromatograohy-mass spectrometry,electron paramagnetic resonance and other methods.It was proved thatα-aminoalkyl radical generated by direct oxidation of tertiary aniline at the anode was an important intermediate in the electrocatalytic oxidation reaction.In addition,density functional theory（DFT）calculations showed thatα-aminoalkyl radical and maleimide were combined to form a ring through a stepwise mechanism,and then dehydrogenated to generate tetrahydroquinoline compound.（2）The Ni Fe-LDH nanosheet electrocatalyst（Ni Fe-LDH/CC）was synthesized on carbon cloth by hydrothermal method.A series of screening and optimization of electrode material,solvent,supporting electrolyte and current and voltage reaction conditions were carried out using triphenylphosphine as substrate.It was found that when the Ni Fe-LDH/CC was used as anode,Pt sheet was used as cathode,and tetrabutyl tetrafluoroborate was used as electrolyte,in Me CN/H₂O（10:1）mixed solvent,under a constant current condition of 5.0 m A for 2 h,triphenyl phosphine oxide was obtained by oxidation of triphenyl phosphine and the yield was 99%.In addition,we verified the universality of the reaction substrate and the reusability of the catalyst.Finally,we analyzed the reaction mechanism and proved that Ni Fe-LDH was first oxidized to produce nickel-iron hydroxyl oxide with stronger oxidation ability,which was used as a real reaction point for triphenylphosphine oxidation.