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.