  Periodic density functional theory has been employed to characterize the
differences in the structural, Lewis acidic and hydrophobic properties of
Sn--BEA and Ti--BEA. We show that the incorporation of Sn increases the Lewis
acidity of BEA compared to the incorporation of Ti. Hence, the present work
gives an insight into the role of Sn in increasing the efficiency of the
oxidation reactions. The results also justify that the percentage of Sn
substituted in BEA is less than Ti. The structural analysis shows that the
first coordination shell of Sn is larger than that of Ti. However, the second
coordination of both sites remains the same. Moreover, the water resistant
properties of these substituted zeolites are quantified.

Materials Science