Abstract: A combined bond-valence and periodic DFT study was carried out to interpret the nature of the d electrons in the active sites of the MoVTeNbO composite oxide catalyst (M1 phase). On investigating all the possible distribution of the coupled d electrons and oxygen vacancies, the most efficient combination of M-M-Te (M = Mo or V) active sites for propane selective oxidation has been argued. Besides, MoO6 octahedra primarily stabilizes the crystal structure of M1 phase by attaining strong covalent Mo–O bonding in the equatorial plane, while VO6 octahedra plays a minor role. Nb species that has been considered to stabilize the M1 phase was found to have mainly ionic inter-actions with the framework and act as a structure-directing agent in forming the pentagonal channels in the M1 phase.

Key words: propane, selective oxidation, molybdenum, vanadium, tellurium, niobium, composite oxide, bond-valence, density-functional theory (DFT), active site