Study On The Preparation And Catalytic Performance Of MOFs And MOFs Based Composite Catalysts

Metal-organic frameworks(MOFs)are consist of a kind of inorganic subunits(metal ions or clusters)and organic linkers forming a three-dimensional well-defined structure.Recently,MOFs have been used for adsorptive removal of various hazardous pollutants from water,such as dyes,herbicides/pesticides,pharmaceutical and personal care products.On the other hand,catalysis by MOFs is a rapidly expanding field due to the unique textural and physicochemical properties of these materials.In this study,four Fe-based MILs and two kinds of MOFs based composites were prepared by hydrothermal and chemical method.In addition,the adsorption and catalytic degradation performance were explored.The main research contents are as follows:(1)Metal-organic frameworks(MOFs)MIL-n(Fe)(n = 101,100,53,and 88B)prepared in the facile solvethermal process were introduced as both adsorbents and catalyst to generate powerful radicals from persulfate for AO7 removal in the water.Various catalysts were characterized by by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),and scanning electron microscopy(SEM).The results indicated that AO7 can be totally degradated in a 240 min reaction by MIL-101(Fe)when initial AO7 concentration was 80mg/L,persulfate concentration was 15 mmol/L,MIL-101(Fe)was 0.2 g/L,and the initial pH was 6.16.The sequence of the materials ability in the combination of adsorption and degradation was MIL-101(Fe)>MIL-100(Fe)>MIL-53(Fe)>MIL-88B(Fe).Moreover,the reactive species in MIL-101(Fe)/persulfate system was identified as sulfate radical and hydroxyl radical.Recycle experiments showed the MIL-n(Fe)were stable and can be reused.Thus,the MIL-n(Fe)/persulfate process may be an effective technology for treating wastewater containing resistant organic compounds.(2)A novel quinone-modified metal-organic frameworks NH2-MIL-101(Fe)was synthesized using a simple chemical method under mild condition.The obtained AQS-NH-MIL-101(Fe)was characterized by FTIR,XRD,SEM,X-ray photoelectron spectra(XPS),cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS).The introduced 2-anthraquinone sulfonate(AQS)can be covalently modified with NH2-MIL-101(Fe)and acts as a redox mediator to enhance the degradation of bisphenol A(BPA)via persulfate activation.The results indicated that AQS-NH-MIL-101(Fe)exhibited better catalytic performance compared with NH2-MIL-101(Fe)and NH2-MIL-101(Fe)with free AQS(NH2-MIL-101(Fe)/AQS)when initial BPA concentration was 60 mg/L,persulfate concentration was 10 mmol/L,AQS-NH-MIL-101(Fe)was 0.1 g/L,and the initial pH was5.76.Moreover,the reactive species in AQS-NH-MIL-101(Fe)/persulfate system was identified as sulfate radical and hydroxyl radical.In addition,the AQS-NH-MIL-101(Fe)catalyst exhibited excellent stability and can be used several times without significant deterioration in performance.Thus,AQS-NH-MIL-101(Fe)/persulfate process may be an effective technology for treating wastewater containing resistant organic compounds.(3)Materials based on phosphotungstic acid(H3PW12O40,HPW)encapsulated in metal organic framework(MOF)MIL-53(Fe)were prepared by a simple solvothermal method.The as-synthesized samples were characterized by XRD,FTIR,SEM,XPS,EIS,energy-dispersive X-ray spectroscopy(EDS)and photocurrent response method.The resulting materials were evaluated in the photodecomposition of cationic dye Rhodamine B(RhB)under visible light irradiation.The results showed that the composites exhibited better photocatalytic activities than pure materials when initial RhB concentration was 20 mg/L,HPW@MIL-53(Fe)was 0.1 g/L,and the initial pH was 4.67.The effect of radical scavengers on the degradation of RhB was also studied,proving that hydroxyl radical is the major radical and holes and O2-·are the assistant radicals in this study.Recycle experiments showed the HPW@MIL-53(Fe)was stable and can be reused.Thus,HPW@MIL-53(Fe)composites/visible light process may be an effective technology for treating wastewater containing resistant organic compounds.