Dual-ligand Metal-organic Frameworks Prepared With DBD Plasma Method And Their Properties Research

Printing and dyeing wastewater and medical wastewater caused by excessive use of H₂O₂disinfection and sterilization during the new crown epidemic not only had a serious impact on the ecological environment,but also caused certain damage to human health.Therefore,realizing the degradation of printing and dyeing wastewater and the efficient and rapid detection of hydrogen peroxide were the top priorities.Metal-organic frameworks(MOFs)were a new class of porous nanomaterials composed of metal ions/ion clusters and organic ligands,which were widely used in catalysis,biosensing and other fields due to their high specific surface area and high porosity.Among them,Fe-MOFs were based on ferric oxide(Fe-O)clusters,which can be excited by visible light as potential photocatalysts for dye degradation;Fe-MOFs can be used as peroxidases with a high cycle rate of Fe²⁺/Fe³⁺,which accelerated the interaction between Fe-MOFs and H₂O₂.Electron transfer was beneficial to improve the catalytic activity of the catalyst,and can realize the colorimetric sensing detection of H₂O₂.However,the further development of Fe-MOFs was limited due to the disadvantages of poor hydrothermal stability,few active sites,and fast photogenerated electron-hole recombination rate.Due to the problems of poor hydrothermal stability and few active sites,designing mainly from three aspects:ligand modification,improved preparation method and morphology regulation.Fe-N-O structure was constructed by introducing the second auxiliary ligand(2-methylimidazole)to modify the ligand,which could expose abundant defects.DBD plasma method can not only shorten the preparation time effectively,but also increased the surface defects.Designing coral-like catalysts with unique angular defects can improve the stability and expose more active sites.S-Fe-MOFs with Fe Cl₃·6H₂O as iron source and trimesic acid(H₃BTC)as organic ligands were successfully prepared by DBD plasma method.D-Fe-MOFs with different ligand ratios and N-Fe-MOFs with different metal and ligand ratios were used as photocatalysts for the photocatalytic degradation of methyl orange.When the discharge voltage was 15.6 k V,the discharge time was 90 min,the metal/organic ligands(Fe/L)molar ratio was 1:2,the BTC/2MI molar ratio was 1:1and the reactant concentration was 12 g/L,the photocatalytic performance was the best.The degradation rate of methyl orange(100 mg/L,1000 m L)could be achieved94%by 0.2 g/L catalyst under UV irradiation for 36 min.The degradation rate of methyl orange(20 mg/L,1000 m L)could be achieved 97%by 0.8 g/L catalyst under visible light irradiation for 48 min.Synthesized dual-ligand MOFs with DBD plasma method can effectively increase the surface defects and expose more active sites,which was an effective method to improve the performance.Fe-HEDP prepared(using Fe Cl₃·6H₂O as iron source and HEDP as organic ligand),Fe-[(HEDP)(2MI)]_xprepared(using Fe Cl₃·6H₂O as iron source,HEDP and2MI as organic ligand)with DBD plasma method,which were used for rapid detection of hydrogen peroxide.The performance of Fe-[(HEDP)(2MI)]_xwith N element was obviously better than that of Fe-HEDP.Under the optimum preparation conditions(discharge voltage 9.5 k V,discharge time 120 min,metal iron/organic ligands mole ratio of 1:1 and HEDP/2MI mole ratio of 1:1),and under the conditions(water bath temperature of 30?,buffer p H of 3.5,TMB concentration of 20 m M and catalyst concentration of 0.7 mg/m L),which could reach enzyme activity more than 92%.The linear relationship of Fe-[(HEDP)(2MI)]₂was good in the range of0-500?M hydrogen peroxide concentration(R~2=0.9978),and the detection limit was80?M.The catalyst with coral-like structure was more stable and less prone to collapse,and the unique structure provided abundant mass transfer channels and exposes more active sites.