Ligand-functionalized And Ag-modified MIL-125（Ti） For Photocatalytic Oxidation Of Ethanol

Converting ethanol into downstream products is one of the important routes of global energy cycle and carbon cycle in the future.Photocatalytic conversion of ethanol has become a hot research topic in recent years because of its mild reaction conditions and less by-products.MIL-125（Ti）is a new type of metal organic framework material.It not only has large specific surface area and uniform pore distribution,but also has good photocatalytic performance.Using MIL-125（Ti）after ligand modification in photocatalytic partial oxidation of ethanol will expands its application scope and has some scientific significance.In this paper,MIL-125（Ti）was synthesized by solvothermal method.The effects of titanium precursor,raw material ratio and ligand doping on MOF catalyst were investigated.The MOF catalyst with excellent performance was modified by Ag,Pt and PD noble metals by impregnation method and ultrasonic method.The phase,electrochemical performance and surface species of the catalyst were characterized by the means of XRD,UV-Vis,SEM,TEM and EIS.The performance of the catalyst for photocatalytic partial oxidation of ethanol in the range of 25℃-45℃was investigated,and the mechanism of the catalytic reaction was preliminarily analyzed according to the results obtained.The conclusions of this study are as follows:1.When the ratio of titanium precursor to ligand is 1:3,the best MOF structure was obtained.2.Doping of H₂BDC-NH₂,H₂BDC-OH,H₄（dobdc）could adjust the light absorption range of the catalyst.Doping H₂BDC-OH,H₄（dobdc）can change the morphology of MIL-125（Ti）.The doping ligand reduced the valence band of MIL-125（Ti）.3.The products of photocatalytic partial oxidation of ethanol on MIL-125（Ti）were acetaldehyde,ethyl formate,ethylene,ethyl acetate and CO₂;MIL-125（Ti）-5OH has the best ethanol conversion rate,reaching 45.52%at 45℃,but when the doping amount of the ligand containing H₂BDC-OH was increased to 10%,the ethanol conversion and the selectivity of acetaldehyde were reduced.4.The photocatalytic performance of the three catalysts loaded with Ag,Pt or Pd was enhanced,and the catalyst loaded with Ag had the best catalytic performance.The loading amount of Ag had a certain correlation with the ethanol conversion and product selectivity.The ethanol conversion of the catalyst loaded with 0.5 wt%Ag was as high as 84.48%and the acetaldehyde selectivity was 76.36%at 45℃.5.The catalyst with lower metal content could be prepared by ultrasonic method.When the metal content was the same,the ethanol conversion and product selectivity of the catalyst prepared by impregnation method were better than that by ultrasonic method.However,ultrasonic treatment could destroyed the structure of MIL-125（Ti）.