Preparation Of Ferrite Base Semiconductor Catalyst By MOF Template Method And Its Photochemical Properties

In recent decades,with the continuous improvement of global industrialization,it has brought good quality of life to human beings,but also caused great harm to the environment.Urgent solutions to energy and environmental problems have become the current situation.Among the existing environmental problems,water pollution has greatly affected people’s life and the survival of creatures in nature.With the emergence of the novel coronavirus in recent two years,the use of various antibiotic drugs has increased more than before,resulting in an increasing number of antibiotics that cannot be metabolized in the environment.Therefore,it is necessary to find a green and environmentally friendly way to remove antibiotics in water.Among all kinds of energy sources,solar energy,which is inexhaustible,is considered to be clean and efficient green energy.Therefore,photocatalytic technology using solar energy to react is the best choice for removing antibiotics from water.Photocatalytic reaction is a kind of reaction that converts light energy into chemical energy by absorbing and utilizing light source by semiconductor,which has the advantages of high efficiency,environmental friendliness and low cost.Although traditional photocatalysts can carry out photocatalytic reactions,their low absorptivity to visible light and high recombination efficiency of photogenerated carrier and hole pair result in weak photocatalytic activity.Therefore,different modification methods should be used to improve the activity of photocatalytic materials.Iron-based semiconductor is considered to be a good material capable of photocatalytic reaction,with appropriate band gap and light absorption range,and by virtue of its natural advantages of magnetism,it has been reported many times in the research field of photocatalytic removal of antibiotics from water.In particular,ZnFe₂O₄in iron-based semiconductor can be used as a good photocatalyst because of its narrow band gap value and high light absorption intensity.However,due to the narrow band gap value of ZnFe₂O₄,photogenerated electrons can easily recombine with holes,so ZnFe₂O₄can be used as substrate material for modification on this basis.The common modification methods are ion doping,heterojunction construction and supported quantum dots.Based on the above,the main work of this paper is as follows:（1）ZnFe₂（C₂O₄）₃nanorods with MOF structure were synthesized by hydrothermal method,and ZIF-8 with MOF structure was grown on the MOF.At the same time,rare earth element Er was doped in the composite to introduce a new impurity level.A MOF-on-MOF hollow nanotube structure was obtained,and the origin of the hollow structure was explained by Ostwald curing mechanism.Finally,the composite ZnFe₂O₄/Er-Zn O was obtained by calcination using MOF-on-MOF as template.After the characterization of morphology,chemical structure,physical properties and photoelectrochemical properties,it is found that the photocatalytic activity and stability of ZnFe₂O₄/Er-Zn O composite is better than that of single ZnFe₂O₄and single Zn O,which is due to the unique hollow nanotube-like structure of ZnFe₂O₄/Er-Zn O.The specific surface area of the material is greatly increased to provide more active sites.The work function,Fermi level and charge density difference of ZnFe₂O₄and Er-Zn O were calculated by density functional theory（DFT）.It is concluded that the heterostructures formed between ZnFe₂O₄and Er-Zn O are formed into Z-type heterostructures,which accelerate the photogenerated carrier migration and inhibit the photogenerated carrier-hole recombination.The degradation efficiency of ZnFe₂O₄/Er-Zn O reached 97%.In addition,the possible degradation route of antibiotics was also analyzed,which provided an idea for the treatment of water pollution.（2）ZnFe₂（C₂O₄）₃precursor nanorods with MOF structure were synthesized by the same method as described above,and then ZnFe₂O₄nanorods were obtained by calcining them,and then a layer of flower-like Bi OI was loaded on the nanorods by hydrothermal method to obtain ZnFe₂O₄/Bi OI composite.Through morphology characterization,chemical structure characterization and photoelectrical properties analysis,it was found that ZnFe₂O₄/Bi OI has a p-n heterostructure,and the photogenerated carrier can be separated well after excitation,which accelerates the migration rate from the internal to the surface of the material,so as to participate in the photocatalytic reaction.In the experimental analysis of photocatalytic degradation of antibiotics,the degradation efficiency of tetracycline（TC）by ZnFe₂O₄/Bi OI photocatalyst reached 94.8%,which could effectively remove TC from aqueous solution and showed excellent cycling stability.