Catalyst modeling
Recent studies suggest that mesoporous silica is a good catalyst support
for metal oxide catalysts. [30] Obviously, in
mesoporous silica, the metal oxide catalyst exits as a nanocluster.
Thus, considering computational cost and accuracy, in the present study,
catalysts were modeled as ultrasmall nanoclusters. For MgO, we adopted
the structure reported in the literature.[31] For
the ZnO cluster model, we replaced the Mg atoms of the
(MgO)16 cluster by Zn atoms and performed geometry
optimization; the optimized structure is shown in Fig. 1 alongside that
of (MgO)16.