Self-formation Phenomenon to Hierarchically Porous Metal Oxides : Design, Synthesis and Application

Over the last decade, tremendous research has been focused on the synthesis and applications of hierarchically porous materials. Hierarchical porous materials have enhanced materials’ properties compared to those with unimodal pore structure. Owing to their structure, a large series of domains have a fervent interest in hierarchically porous materials. This thesis is aimed at designing a new reaction system to develop hierarchically porous metal alkoxides with novel porosities via a spontaneous self-formation procedure. Furthermore, this thesis is also aimed at investigating the possible formation mechanism based on the self-formation procedure, and also the photocatalytic performance and adsorption capacity of the hierarchically porous metal alkoxides. The objective of this thesis is to fabricate a series of hierarchically porous materials with different porosities by adjusting the spontaneous self-formation procedure from metal alkoxides via novel strategies. In this thesis, we developed a novel water-adjusting method in order to adjust the amount of water in the reaction system thus controlling the self-formation procedure. Acetonitrile and methanol were used as the examples to be the reaction mediums here. On the basis of this novel strategies, a series of metal oxides with diverse porous structures had been synthesized, which would be suitable for a variety of applications from catalysis, to separation or environmental remediation. The evolution of the porosity of textural properties of metal oxides, formed from the addition of metal alkoxide to a water-acetonitrile system, with increasing water content was carefully investigated and summarized. The formation mechanism of hierarchically porous metal oxides in a water-acetonitrile system had been discussed in detail. Furthermore, the spontaneous self-formation process to form hierarchically porous titania in methanol was also studied in this thesis. More importantly, the hierarchically 3D dendrimeric nanostructures formation process had been successfully investigated in situ by optical microscopy from Leica microsystem. The resultant hierarchically porous metal oxides were used as photocatalysts and adsorbents for dye molecule depollution and presented very high activities. In addition, hydrothermal and surfactant treatment to enhance the photocatalytic activity of hierarchically meso-macroporous titanias was also demonstrated in this thesis.