| Polyoxometalates(POM)is a type of important chemical that can be used in biomedical engineering,energy storage,supramolecular chemistry and catalysis,because of its special structure,as well as its physical and chemical properties.POM can perform multi-electron redox reaction due to the multiple valence combination of atoms in its structure.It can act as a strong oxidant or even as an oxidation-reduction bifuncaional catalyst.POM has important applications in the field of catal ytic engineering.However,the unmodified pure POMs have some drawbacks,such as low solubility in organic solvents,unstability,difficulty in recovery,relatively small pore size,and small specific surface area(BET).The modification of POMs has become a hot topic in reseach to obtain a catalyst with better performance and easier regenerationBenzaldehyde(Bz H)is a kind of important chemical intermediate.The traditional preparation processes of benzaldehyde are benzyl chloride hydrolysis or toluene oxidation.Nevertheless,the benzaldehyde hydrolysis method will cause residue chlorine in the product,and the toluene oxidation method has low selectivity of Bz H.In order to solve the problems of residue chlorine and low selectivity,the preparation of benzaldehyde with high selectivity by finding the appropriate reaction materials is a scientific topic worth studying.The derivatives of benzophenone have important value in biomedicine,as well as in the optical materials.They have been widely used in the optical devices and photopolymerization reactions.A large number of researches have been conducted on the synthesis methodology of benzophenone derivatives.P-aminobenzophenone derivatives(p-ABPs)have the structures containing amino groups,which can be modified to get more complex and popular benzophenone derivatives.It is harder to synthesis the p-aminobenzophenone than the other benzophenone derivatives without amino group(-NH2).Thus,the exploration of p-ABPs synthesis methods has great significance.In order to solve the above problems,two types of novel coumarin-surfactant-modified POM((Coumarin)4PMo11VO40 and(Coumarin)3HPMo11VO40)were prepared in this research.Their catalytic effects were tested in benzyl alcohol selective oxidation reaction.The conversion rate of benzyl alcohol is more than 98% and the selectivity of benzaldehyde is 100% under the reaction condition of(Coumarin)3HPMo11VO40 as the catalyst and air as the oxidant.Based on this study,a new method was developed to synthesize p-aminobenzophenone from the benzyl alcohol derivatives and the aniline derivatives.There is no need to protect the amino group during this reaction.This approach has the advantages of mild reaction conditions,simple operation,high reaction selectivity and good resistance of functional groups.The details are:1.A cationic surfactant molecule containing coumarin structure units was synthesized.Then,two kinds of coumarin-surfactant modified POM were prepared by ion exchange between the coumarin-surfactant and counter ions of unmodified POM.Their structures were characterized by NMR,FT-IR,TG,EA,XRD and SEM.2.Two kinds of POM modified by coumarin surfactants were applied to the selective catalytic oxidation reaction of benzyl alcohol.The catalytic effects of these two catalysts were studied by comparing adsorption kinetics between catalyst s and reactant,the BET and pore diameter of different catalysts.The results showed that the specific surface area and pore size of coumarin surfactants with rigid structure are larger than those of unmodified polyacids and those POMs modified by small molecule surfactants with flexible chain.3.The electrochemical analysis was used to investigate the difference between POM and coumarin-surfactant modified POM in cyclic voltammograms(CVs).The results of CVs further explained the reason of activity differences.It also revealed that the diffusion of coumarin surfactant modified POM on the electrode surface is a surface controlled process.4.After the research of selective catalytic oxidation reaction of benz yl alcohol,we used the benzyl alcohol and amino-non-protected aniline as raw materials to synthesize p-aminobenzophenone by catalytic reaction of(Coumarin)3HPMo11VO4.Following this reaction as a template,we also managed to synthsize a series of p-aminobenzophenone deritives with different functional groups.The reaction results show that the reaction conditions are mild,environment-friendly,and the functional groups are well tolerated.At the same time,several reaction mechanism control experiments were conducted,and the possible reaction mechanism was proposed.5.The molecules containing coumarin groups have photo-responsive properties under UV,which can undergo photodimerization.The photodimerization behavior of coumarin surfactant-modified surfactante is confirmed by UV exposure experiments.The results prove that this novel type of catalysts are expected to achieve homogeneous catalysis and heterogeneous separation... |
