Preparation And Photocatalytic Properties Of Iron Based Metal Organic Framework Composites

In recent years,people are increasingly concerned about the two topics of environmental pollution and energy crisis.Water pollution is the most representative environmental pollution problem.It is difficult to avoid the discharge of large amounts of industrial wastewater from industrial production,with the discharge of dye wastewater causing the most serious pollution to the environment.Metal-organic backbones（MOFs）are very popular in the environmental and energy fields and,in line with expectations,show good results in photocatalysis.Although iron-based MOFs are widely used in photocatalytic degradation of pollutants,they suffer from problems such as poor water stability and fast photogenerated electron-hole complexation,which greatly limit their application in photocatalytic treatment of wastewater.Therefore,in this paper,on the one hand,the metal-organic skeleton MIL-101（Fe）was used as the raw material and doped with Zn²⁺to form the bimetallic MIL-101（Fe-Zn）composite photocatalytic material;on the other hand,Bi₂Mo O₆and MIL-101（Fe）were combined to form the Bi₂Mo O₆@MIL-101（Fe）composite material,thus further improving the Fe based metal-organic skeleton of the photocatalytic performance.The details of the study are as follows:（1）In this paper,a bimetallic MIL-101（Fe-Zn）composite photocatalytic material with Zn²⁺-doped MIL-101（Fe）was prepared by a simple one-step solvothermal method using ferric trichloride hexahydrate,terephthalic acid and zinc nitrate hexahydrate as raw materials.The materials were characterised using XRD,SEM,XPS,UV-Vis DRS and FT-IR,and the analysis proved that the bimetallic MIL-101（Fe-Zn）composite photocatalytic materials were successfully synthesised.The experimental data showed that0.02 g of Zn²⁺-doped MIL-101（Fe-Zn）composite photocatalytic material and 0.2 m L of H₂O₂at a concentration of 50 m L of rhodamine B（Rh B）could achieve 96.5%degradation efficiency after 180 minutes of irradiation under visible light.The degradation efficiency of CR solution without the addition of H₂O₂under the same conditions could reach 93.4%,which was much higher than the degradation rate of MIL-101（Fe）for both organic dye solutions.The results indicate that the doping of Zn²⁺in bimetallic MIL-101（Fe-Zn）expands the photoresponse range of the material,which can inhibit the compounding of photogenerated electrons and holes,effectively increasing the photometric yield and thus enhancing the degradation of organic dye wastewater.The degradation efficiency of the bimetallic MIL-101（Fe-Zn）composite photocatalytic material was maintained high after five experimental cycles,indicating its high stability and reusability.Finally,the photocatalytic mechanism of the bimetallic MIL-101（Fe-Zn）composite photocatalytic material was tentatively proposed.（2）In this paper,Bi₂Mo O₆@MIL-101（Fe-Zn）composite photocatalytic materials were prepared by a two-step solvothermal method using ferric trichloride hexahydrate,bismuth nitrate pentahydrate,sodium molybdate dihydrate and terephthalic acid as raw materials.Specific analyses were carried out using SEM,XRD,XPS,FT-IR and UV-vis characterisation to demonstrate the successful synthesis of Bi₂Mo O₆@MIL-101（Fe）composite photocatalytic materials.Congo red（CR）was used as the target dye wastewater and the photocatalytic degradation effect of the composite material on the dye wastewater was investigated.From the experimental data,it can be seen that:after 30 min reaction in the dark and 180 min irradiation under visible light,0.01 g Bi₂Mo O₆@MIL-101（Fe）composite photocatalyst was put into 50 mg/L concentration of 50 m L of Congo red（CR）simulated organic dye The degradation efficiency of the CR solution could reach 93.4%,which was much higher than that of MIL-101（Fe）degradation of CR solution.The material effectively suppressed the compounding of photogenerated electrons and holes,increasing the yield of light quanta and thus enhancing the ability to degrade organic dye wastewater.The photocatalytic mechanism of the Bi₂Mo O₆@MIL-101（Fe）composite photocatalytic material is tentatively proposed.