How TeO Defects in the MoVNbTeO Catalyst Material Affect the V4+ Distribution: A Computational Study

We studied computationally the effects of TeO defects on the distribution of reduced centers, V4+, in the MoVNbTeO M1 bulk material. To this end, we selected a distribution of V and Mo centers, constructed models with periodic boundary conditions, and applied a hybrid DFT approach. We identified two main factors that determine the stability of specific V4+ sites as follows: (i) The proximity of a [TeO]2+ moiety increases the tendency for reducing specific vanadium sites. (ii) The stability of the system is affected by the types and numbers of polaron–polaron interactions in which V4+ centers participate. Higher energy penalties result when a reduced center, V4+, is located in the vicinity of a [TeO]2+ vacancy, suggesting an increased propensity of finding fully oxidized vanadium centers, V5+, close to vacant hexagonal channels. We also present linear models that predict the energetics of systems where all channels are filled by TeO as well as when one channel is void of TeO. As fully oxidized V centers, V5+, are considered pertinent to the partial selective oxidation catalysis of short alkanes, tuning the TeO defect density may be crucial for such applications.