Computational study of metal-free N-doped carbon networks as hydrogenation catalysts

The future development and assesment of an industry more environmental friendly will include the use of metal-free catalysts. Most of the reported metal-free catalysts are homogeneous and often their recycle is difficult; therefore, develop and investigate them is of interest both theoretical and experimental. Recently, N-doped nanotubes and graphene sheets, were synthesized [1,2], and it was demonstrated that the incorporation, within these carbon structures, of nitrogen atoms causes a greater electron mobility and introduces more active sites for catalytic reactions. This investigation is aimed at elucidating the main features of the hydrogen fragmentation over these carbon frameworks. Several models and different theoretical approaches were employed in this investigation to characterize the structure and properties of nitrogen pyridinic moieties framed within a carbon network, commonly classified as pyridinic defects. Two different kinds of pyridinic defects configurations within a carbonaceous environment were studied. The influence of the size of the π-system and of the curvature on the ergonicity associated to the H2 bond cleavage were analyzed. It was found that increasing the number of the benzene rings surrounding the defect the ergonicity of the reaction increases whereas the curvature of the carbon network scarcely affects this quantity.