Easy and flexible preparation of nanocasted carbon monoliths exhibiting a multimodal hierarchical porosity

Carbon monoliths exhibiting two- or three-modal porosity, in addition to the inherent microporosity, have been prepared by nanocasting using meso-macroporous silica monoliths as the scaffold. Volume and surface templating has been successfully combined in a one-step impregnation approach, which is shown to be a straightforward means to impregnate the smaller modes of pores in the silica host. The monoliths were investigated by N-2-sorption, scanning electron microscopy, transmission electron microscopy, and mercury porosimetry, resulting in a fairly complete description of the origin of the different modes of porosity in the system. It is shown that the carbon monoliths represent a positive replica of the starting silica monoliths on the micrometer length scale, while the volume templated mesopores are a negative replica of the silica scaffold. 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. (C) 2004 Elsevier Inc. All rights reserved.