Exotemplate methods

In this chapter, we provide an overview of the recent research and development in the preparation, characterization, and application of novel porous carbons using both the endotemplate and the exotemplate methods. A discussion of zeolite templates for microporous carbons is followed by that of ordered mesoporous silica templates for OMCs, nanoparticle templates for mesoporous carbons, sol-gel processed porous carbons, self-assembled colloidal crystal templates for ordered macroporous carbons, and colloidal sphere templates for hollow carbon spheres, as well as other templating approaches to preparing carbon nanostructures. Then,... 

The syntheses of ordered mesoporous solids discussed above are classified as endotemplate methods (or soft matter templating ). In the case of exotemplate methods ( nanocasting or hard matter templating ), no soft surfactant template is used. Instead, the pore system of an ordered mesoporous solid is used as template itself, serving as a mold for preparing varieties of new mesostructured materials [38]. 

On the other hand, the soft template method involves cooperative assembly between the structure-directing agents (usually surfactants) and organic precursor species in solution. Therefore, the carbon structures obtained via soft templating are more flexible and their formation is dependent on temperature, type of solvent and ionic strength. However, there are currently only limited examples for the successful fabrication of porous carbon via the soft template method, which were reviewed recently by Wan et alP Soft template and hard template routes have been classified as endotemplate and exotemplate, respectively. 

Very simple method An important benefit of this spontaneous self-formation procediu-e is its simplicity. Hierarchically porous materials can be obtained by just dropping the liquid metal alkoxide precursors into an aqueous solution, without any posttreatment such as calcination or solvent extraction to remove the exotemplate. Fiuthermore, the spontaneous self-formation pro-cediu-e generally takes place at room temperature in an open system. This feature allows the scaling up of this method, which is quite desirable in industry. 

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