MCM-41, The Synthesis And Characterization Of The Performance / MIL-101 Surface-modified Titanium Dioxide Material

TiO2has attracted more attention due to its high photocatalytic activities among the semiconductors photocatalytic materials. However, photocatalytic activity of pure TiO2is decreased because of its lower specific surface area and small powder particle size. Recently, some studies showed that porous materials diplayed significant photocatalytic activity when transition metal compounds were highly dispersed on the surface or within the framework of the materials. Grafing titanium compounds on the surface of porous materials is therefore an practical method to prepare photocatalytic materials. The sol-gel technique is the traditional method for introduction of transition metal ions into the pores of materials. The as-prepared materials have, however, the disadvantage of no well-defined catalytic centers, leading to difficulty in investigation for catalytic mechanisms. Surface organometallic chemistry (SOMC) has greatly promoted the development of catalytic discipline through decades of research. The SOMC method is a novel technique for introduction of transition metal ions into the porous materials. SOMC is devoted to the study of the reaction of organometallic complexes with solid surface of materials and the subsequent processing, which can generate materials with well-defined active centers on the surface and special catalytic properties. Therefore, this new method can dispose of the problems met by the traditional sol-gel method. SOMC has gradually become a hotspot in the catalysis field.In this thesis, the titania-modified porous materials MCM-41and MIL-101were prepared by SOMC method and structurally characterized by FT-IR, TEM, EDAX, XPS, XRD and TG techniques. Their photocatalytic activities for degradation of methyl orange solution were investigated. The main contents of this theis are:(1) Taking tetrakis(dimethylamino)titanium as precursor and grafting it on the surface of pretreated MCM-41at500℃, by the SOMC method, the surface-modified molecular sieve materials by TiO2with different times were prepared, these samples were named as MCM-41/(TiO2)(1), MCM-41/(TiO2)(2), MCM-41/(TiO2)(3), MCM-41/(TiO2)(4) and MCM-41/(TiO2)(5), respectively, based on the modification times. These samples were characterized by FT-IR, TEM, EDAX, XPS, XRD and TG. The results showed that titanium exists as Ti(Ⅳ) species on the surface of MCM-41and titanium concentration increasses with increase of modification times. In addition, with the increase of the times of surface modification, titanium content was also increased. And on the MCM-41surface no crystalline TiO2species appeared, indicating that the titanium dioxide presents as highly dispersed form on the zeolite surface. And the pore structure of molecular sieve remains its completeness after the high-temperature activation treatment.(2) Taking tetrakis(dimethylamino)titanium as precursor and grafting it on the surface of pretreated MIL-101at150℃, by the SOMC method, the surface-modified MIL-101by TiO2were prepared, this sample was named as MIL-101/TiO2and characterized by FT-IR, TEM, EDAX, XPS, XRD and TG. The results showed that titanium exists as Ti(IV) species on the surface of MIL-101and on the MIL-101surface no crystalline TiO2species appeared, indicating that the titanium dioxide presents as highly dispersed form on the zeolite surface. In addition, MIL-101remains its full octahedral structure after the activation treatment.(3) Photocatalytic properties of different samples were investagated for the degradation of methyl orange solution. In addition, the influence of catalyst amount and initial concentration of the dye solution for the photocatalytic reaction were studied. The results indicated that both MCM-41/(TiO2)(2) and MCM-41/(TiO2)(3) have better decolourization abilities for methyl orange on comparison with other samples; MIL-101/TiO2shows photocatalytic activity, too.