Preparation And Catalytic Oxdation Performance Of Metal Complexes Functionalized PMOs

Periodic mesoporous organosilicas (PMOs) represent an exciting new class of organic-inorganic nanocomposites with highly ordered pore networks and large internal surface areas. Different from ordered mesoporous silicas, PMOs have a uniform distribution of organic groups both within the pore walls and on the pore channel surface. The introduction of organic bridging groups not only can tune the chemical and physical properties of the mesoporous materials and improve the hydrothermal and mechanical stability, but also provide an effective approach to the construction of highly functionalized mesoporous materials. Hence, PMOs have been applied to many fields, such as adsorption, catalysis, separations, detection, etc. In this thesis, metal complexes functionalized PMOs were prepared and their catalytic oxidation performances were also investigated. It is expected that the research can provide theoretical and practical basis for the preparation of new functionalized hybrid materials and excellent catalysts. The main research contents in this thesis are as follows:(1) PMOs materials containing different amounts of phenyl bridging groups have been synthesized in the synthesizing system with different TEOS/BTEB ratios by hydrothermal method and were characterized by XRD and nitrogen adsorption-desorption. The results showed that as-synthesized PMOs exhibit a typical SBA-15-like mesoporous characteristics with high surface area and narrow pore size distribution. The amounts of BTEB in the synthesizing system have influence on the textural properties of the as-synthesized PMOs.(2) CH2Cl-PMOs were synthesized by chloromethylation of phenylene moieties in the framework of PMOs, and V-PMOs catalysts were obtained by grafting vanadium-Saldien on CH2Cl-PMOs. The samples were characterized by XRD, nitrogen adsorption-desorption, UV-vis and elemental analysis. The results showed that vanadium-Saldien complexes can be successfully immobilized on the PMOs by this route, and the prepared V-PMOs still retain the mesoporous structure. For comparison, vanadium-Saldien complexes functionalized SBA-15(V-SBA-15) was prepared by the similar method. The catalytic properties of different materials were investigated by using the cyclohexane oxidation as a model reaction. In solvent-free aerobic reaction system, V-PMOs not only showed higher catalytic activity, but also higher stability than V-SBA-15.(3) Cu-PMOs catalysts were obtained by grafting copper-Saldien on CH2Cl-PMOs. The samples were characterized by XRD, nitrogen adsorption-desorption, UV-vis and elemental analysis. The results showed that copper-Saldien complexes were successfully immobilized on the PMOs, and the materials after functionalization by chloromethylation and immobilization of metal complexes remain the mesostructural characteristics, although the order decreased. Similarly, Cu-SBA-15catalytic material was also prepared by modification of SBA-15with3-chloropropyltriethoxysilane and then grafting Cu-Saldien. The catalytic performances of different materials in cyclohexane oxidation and phenol hydroxylation were investigated. In cyclohexane oxidation reaction with H2O2as oxidant and acetonitrile as solvent, Cu-PMOs have a higher stability than Cu-SBA-15. But in phenol hydroxylation with water as solvent, the stabilities of both catalysts are not satisfied.