Development of novel mesoporous silica and carbon materials

The aim of this project was to develop new route to silica and silica based materials through utilizing green techniques and demonstrate its following applications. Due to the properties of supercritical fluids including high diffusivity, low dynamic viscosity and low surface tension, supercritical fluid (SCF) is becoming a potential alternative solvent class in materials chemistry. The physical properties of SCF could be tuned to more liquid- or more gas- like thus providing an enhanced selectivity of the solubility performance of SCF. Several conditions such as reaction time, pressure and temperature were have been taken into consideration for the synthesis of a spherical mesoporous silica using supercritical carbon dioxide as solvent. Bio-oil has successfully been utilized to prepare carbon-silica composites (CSCs) from mesoporous silicas. These CSCs comprise a thin film of carbon dispersed over the silica matrix and exhibit porosity similar to parent silica with BET surface areas ranging from 39 to 636 m2/g and pore volumes ranging from 0.03 to 0.31 cm3/g. The surface properties of resulting materials can be simply tuned by the variation of preparation temperatures leading to a continuum of functionalities ranging from polar hydroxyl rich surfaces to carbonaceous aromatic surfaces. The as-synthesised CSC was subsequently used as solid support for the deposition of palladium nanoparticles to catalyse the Heck reaction. This CSC catalyst exhibited a high catalytic activity and excellent reusability for the Heck reaction using either conventional solvent NMP or propylene carbonate. It should be noted that a side product - methyl 3,3-diphenylacrylate was generated during the reaction using CSC catalyst in propylene carbonate with the yield of up to 15.5%. The CSCs were also used to prepare carbonaceous materials by silica etching process. After silica removal, a mesoporous carbonaceous material with the morphology ranging from rod-like to tubular-like could be synthesised.