Selective Catalytic Oxidation Of Alcohols On Magnetic Composites Via Surface Coordination

Selective oxidation of alcohol to corresponding aldehyde has been one of the hot topics in the studies of chemists.Based on the surface coordination catalysis,this dissertation developed catalytic systems which can be recycled many times based on copper salt supported by the magnetic Fe3O4.These catalytic systems employed air as the oxidant and proceeded selective oxidation of alcohols efficiently under mild conditions.The main content includes the following two aspects:In the first part,core-shell Fe3O4@Cu2O and Fe3O4@Cu2O-Cu nanomateria ls for aerobic oxidation of benzylic alcohols are reported with 2,2,6,6-tetrameth ylpiperidine-N-oxyl(TEMPO)and N-methylimidazole(NMI)as the co-catalysts.To anchor Cu2O nanoparticles around the magnetic particles under solvotherm al condition,the magnetic material Fe3O4 was modified by grafting a layer of L-lysine(L-Lys)to introduce-NH2 groups at the surface of the magnetic parti cles.With amine groups as the anchor,Cu(NO3)2 was used to co-precipitate th e desired Cu2O by using ethylene glycol as the reducing agent.Prolonging rea ction time would lead to over-reduced form of the magnetic materials with the presence of copper,Fe3O4@Cu2O-Cu.The nanomaterials and its precursors we re fully characterized by a variety of spectroscopic techniques.In combination with both TEMPO and NMI,these materials showed excellent catalytic activiti es in aerobic oxidation of benzylic alcohols under ambient conditions.For mos t of the benzylic alcohols,the conversion into aldehydes were nearly quantitati ve with aldehydes as the sole product.The materials were recyclable and robu st Up to 7 repetitive runs,its activity dropped less than 10%.The over-reduc ed materials,Fe3O4@Cu2O-Cu,exhibited slightly better performance in the dura bility.The magnetic property allowed easy separation after reaction by simply applying an external magnet.The second part is mainly concerned with the catalyst with Cu2S loading on magnetic Fe3O4 and its catalytic activity on the oxidation of alcohols.In this paper,Fe3O4@Cu2-xS and Fe3O4@CuS magnetic composite materials were synthesized and their catalytic properties were compared.The results indicated that the monovalent copper on the surface of the material play a vital role on selective oxidation of alcohols.Fe3O4@Cu2-xS shows good stability on both structure and catalytic activity,which confirmed by many spectral characterizations including XRD,TEM,XPS,etc.Meanwhile,the catalytic properties of three kinds of Cu2O nanoparticles w ith different morphology were compared by controlled synthesis.We found that the morphology of Cu2O has a certain effect on the selective oxidation of alc ohols and the regularity of catalytic activity was obtained as follows:Cu2O(Octa hedron)>Cu2O(Dodecahedron)>Cu2O(Cube)? Cu2O(Commercial).