Monomeric vanadium oxide: a very efficient species for promoting aerobic oxidative dehydrogenation of N-heterocycles

Abstract

Monomeric active species are very interesting in heterogeneous catalysis. In this work, we proposed a method to prepare VO_x–NbO_y@C catalysts, which involve the one-pot hydrothermal synthesis of inorganic/organic hybrid materials containing V/Nb followed by thermal treatment under a reducing atmosphere. The prepared catalysts were characterized using different techniques, such as high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine structure spectroscopy. It was shown that monomeric VO_x species were dispersed homogeneously in the catalysts. The VO_x–NbO_y@C catalysts displayed high performance in the aerobic oxidative dehydrogenation of N-heterocycles to aromatic heterocycles. It was demonstrated that the selectivity of reaction over the catalyst with a very small amount of V (0.07 wt%) was much higher than that over the NbO_y@C, and the catalyst also exhibited excellent stability in the reaction. The detailed study indicated that monomeric VO₂ species were the most effective for promoting the reaction.