Experimental and atomistic simulation study of the structural and adsorption properties of Faujasite zeolite-templated nanostructured carbon materialst

Nanostructured carbon materials were obtained by templating faujasite zeolites. This was achieved by liquid infiltration of furfuryl alcool and chemical vapor deposition of propylene and acetonitrile. These carbon materials were characterized by adsorption of gaseous nitrogen and carbon dioxide, and the carbon structure was investigated by X-ray diffraction (XRD). They exhibit a very large pore volume in the micropore region (i.e., narrower than 2 nm), and the XRD spectra show the presence of a nanostructured carbon material with a well-defined unit cell whose size and symmetry are imposed by the zeolite template. We made use of Grand Canonical Monte Carlo simulation of carbon adsorption in order to obtain numerical models of such materials and study their texture and mechanical and adsorption properties on an atomistic scale. The carbon-carbon interactions were modeled within the frame of the tight binding and the reactive bond order (REBO) formalisms, while carbon-zeolite interactions were assumed to be relevant to physisorption and described with the PN-trAZ potential. This simulation strategy allowed us to obtain numerical replica that are well-ordered and the opposite of the original 3D zeolite porosity. The numerical samples obtained at various temperatures are made of curved surfaces containing almost exclusively Sp(2) carbon atoms and are very rigid and stiff. The calculated structure factor of such a numerical sample exhibits features that are present in the experimental diffractograms, hence validating the nanocasting procedure. However, the comparison between simulated nitrogen adsorption isotherms at 77 K with experimental values lead us to understand that the real material is defective and contains cavities of a few nanometers in size, larger that those of the perfect original numerical samples. Finally, we found from both experiment and simulation that pure carbon replicas of faujasite zeolite that have optimized pore dimensions are not good candidates for hydrogen Storage at room temperature and moderate pressures, allowing us to draw general conclusions on the use of porous carbon for such an application.