Highly Porous Composites of Metal Oxide and Silicate Nanoparticles for Catalysis

摘要

Transition metal oxides are widely used as catalyst or catalyst supports. Catalytic reactions take place on the surface of catalysts, thus large specific surface area of metal oxide generally lead to superior catalytic activities. But the synthesis of metal oxides with large surface area is relatively complicated and costly. Here we report a generalised synthesis of highly porous composite structures of metal oxide and silicate particulates that are several nanometres in size, from aqueous solutions of metal salts and dispersion of a synthetic clay, laponite. The synthesis involves coupled processes: acid leaching of the clay sheets by the metal hydrate of a strong acidity and the hydrolysis of the metal hydrate species due to the high pH of the clay suspension. As result, the clay layers do not exist in the products. This is distinctly different from the conventional pillaring process and synthesis of porous clay heterostructures (PCHs), during which the clay retains its layer structure. In the product solids, metal oxide and silicate particles are two inter-dispersed phases on a scale of several nanometres, forming a porous composite structure. Therefore, large surface area of metal oxide is available for the reactant molecules.