Study On Preparation Of Fe-MOF Composite And Its Photocatalytic Degradation Of RhB

The discharge of dye wastewater not only damages the ecological environment but also poses a threat to human health.Efficient degradation of dye wastewater is receiving increasing attention.Due to its mild reaction conditions,strong oxidation capacity,and wide treatment range,photocatalytic oxidation is a dye degradation method with broad application prospects.Semiconductor materials and metal-organic framework（MOF）materials can produce strongly oxidizing substances under light irradiation and are the main choices for photocatalysts.Among them,iron-based MOF（Fe-MOF）is favored due to its low cost,environmental friendliness,and unique physical and chemical properties.However,its weak visible light absorption coefficient hinders its application in the field of photocatalysis.In this paper,two new composite photocatalytic materials NH₂-MIL-68(In_αFe_1-α)/PAA and BiOBr/NH₂-Fe-MOF were prepared by combining Fe-MOF with polymer carriers or semiconductor materials.Their structures,morphologies,elemental compositions,and photoelectrochemical properties were studied,and their photocatalytic degradation performance of Rhodamine B（Rh B）was investigated to explain the degradation mechanism.The main contents of the paper are as follows:（1）Spherical carrier material polyacrylate（PAA）microsphereswere prepared by high internal phase emulsion templating method,and NH₂-MIL-68(In_αFe_1-α)/PAA was prepared by impregnation method and one-step solvothermal method to prepare bimetallic MOF composite photocatalytic material.When the molar ratio of indium and iron ions in precursor solution was 7:3,the catalyst dosage was 0.83 mg/L,and the initial concentration of Rh B was 10 mg/L,the degradation rate of Rh B under visible light for 120 min was99.2%,and the reaction rate constant reached 0.03574 min^-1.The photocatalyst had good cyclic stability.The structural morphology characterization showed that the particle size of NH₂-MIL-68(In_αFe_1-α)grown in-situ within the PAA confinement space was reduced by about 90%,exposing more metal center active sites and shortening the diffusion distance.UV-vis DRS,transient photocurrent response,and electrochemical impedance spectroscopy test indicated that the composite material had higher visible light utilization and electron-hole pair separation ability.Free radical capture experiments and ESR testing demonstrate that the main active species in the photocatalytic reaction of the composite material was h⁺,and a possible photocatalytic degradation mechanism was proposed.（2）In order to further improve the efficiency of photocatalytic degradation,BiOBr/NH₂-Fe-MOF composite photocatalytic materials were prepared using a solvothermal method.The composite material had a 3D flower-like microstructure,which achieved a tight combination between NH₂-Fe-MOF and BiOBr,forming a Type II heterogeneous structure,increasing more active sites,improving the utilization of visible light,and promoting the separation of electron-hole pairs.The results showed that when the molar content of NH₂-Fe-MOF was 40%,the catalyst dosage was 0.5 mg/L,and the initial concentration of Rh B was 30 mg/L,BiOBr/NH₂-Fe-MOF achieved the best degradation performance for Rh B,with a degradation rate of 98.2%in 40 min under visible light.Its rate constant k value was 0.08507 min^-1,which was better than the literature data currently reported.The study of photocatalytic mechanism showed that superoxide radicals（·O₂^-）played a major role in the photocatalytic degradation process.