Combined Surface and Volume Templating of Highly Porous Nanocast Carbon Monoliths

Abstract

Nanocast carbon monoliths exhibiting a three- or four-modal porosity have been prepared by one-step impregnation, using silica monoliths containing a bimodal porosity as the scaffold. Combined volume and surface templating, together with the controlled synthesis of the starting silica monoliths used as the scaffold, enables a flexible means of pore-size control on several length scales simultaneously. The monoliths were characterized by nitrogen sorption, scanning electron microscopy, transmission electron microscopy, and mercury porosimetry. It is shown that the carbon monoliths represent a positive replica of the starting silica monoliths on the micrometer length scale, whereas the volume-templated mesopores are a negative replica of the silica scaffold. In addition to the meso- and macropores, the carbon monoliths also exhibit microporosity. The different modes of porosity are arranged in a hierarchical structure-within-structure fashion, which is thought to be optimal for applications requiring a high surface area in combination with a low pressure drop over the material.