Spontaneously formed porous and composite materials
In recent years, a number of routes to porous materials have been developed which do not involve the use of pre-formed templates or structure-directing agents. These routes are usually spontaneous, meaning they are thermodynamically downhill. Kinetic control, deriving from slow diffusion of certain species in the solid state, allows metastable porous morphologies rather than dense materials to be obtained. While the porous structures so formed are random, the average architectural features can be well-defined, and the porosity is usually highly interconnected. The routes are applicable to a broad range of functional inorganic materials. Consequently, the porous architectures have uses in energy transduction and storage, chemical sensing, catalysis, and photoelectrochemistry. This is in addition to more straightforward uses deriving from the pore structure, such as in filtration, as a structural material, or as a cell-growth scaffold. In this feature article, some of the methods for the creation of porous materials are described, including shape-conserving routes that lead to hierarchical macro/mesoporous architectures. In some of the preparations, the resulting mesopores are aligned locally with certain crystallographic directions. The coupling between morphology and crystallography provides a macroscopic handle on nanoscale structure. Extension of these routes to create biphasic composite materials are also described.
Additional Information© 2010 Royal Society of Chemistry. Received 31st July 2009, Accepted 29th October 2009. First published as an Advance Article on the web 10th December 2009. This work was principally supported by the donors of the Petroleum Research Fund of the American Chemical Society. SAC thanks Air Products & Chemicals, Inc. and the UC Discovery program for financial support. EST thanks the Beckman Foundation for a post-doctoral fellowship.
Published - Corr2010p7116J_Mater_Chem.pdf