Influence of the carbon precursors on the structural properties of EMT-type nanocasted-carbon replicas

Abstract

Nanocasted ordered microporous carbons are interesting candidates for studying specific properties related to applications where materials with tailored microporosity and controlled composition are required. In order to extend the choice of these model materials, a systematic study of the nanocasting process was performed using the original and non commercial zeolite EMC-2 (EMT-structure type) as a mould. The influence of the preparation routes on the structural properties of the carbon replicas was more specifically examined using acetylene, furfuryl alcohol and acetonitrile as carbon precursor with a single or double infiltration procedure. It appears, whatever the precursor, that optimized infiltration processes with a carbon filling content above 0.2 g/g of carbon composite yield to faithful carbon replicas with an ordered microporosity. These materials exhibit a high specific surface area (>2500 m 2/g) and a high micropore volume (1.3–1.6 cm 3/g) with nearly no mesoporosity. The pore size distribution, calculated with the NLDFT method from nitrogen physisorption data at −196 °C, shows maxima at 1.0 and 1.8 nm. The first maximum has been attributed to the porosity arising from the nanocasting of the zeolite framework and the second to the incomplete carbon filling of the mould. A strong adsorption capacity at low relative pressure has also been detected when acetonitrile was used as carbon precursor. The degree of the structural organization of the porosity was followed with the first three XRD diffraction peaks characteristic of the hexagonal symmetry of the EMT mould.