Group V metal substitution in silicate model zeolites: In search for the active site

► The molecular structure of the group V sites (V, Nb, and Ta) in zeolite materials become more hydrophobic and less reducible descending the column of the Period Table. ► The stable site with TO group for T = V, transforms into a site with T-OH group for T = Ta. For niobium both sites with Nb-OH and NbO groups are in competition with each other, especially in hydrated conditions. ► Lewis acid base pairs (T+ and TO−) are expected to be present in Nb and Ta dehydrated zeolites.