On the Possibility of Mo Substitution in Mesoporous Materials - Cluster Model Calculations

Rohit Kumar Rana and B. Viswanathan

Department of Chemistry Indian Institute of Technology, Madras 600 036, India.


Scattered Wave SCF-Xa calculations were carried out on various Mo-containing cluster models in order to find out the possibility of molybdenum incorporation in a zeolitic framework, containing ring systems as secondary building units. Four and six membered ring clusters were found to stabilize molybdenum in their framework compared to that by linear chain models. Comparison of relative stabilization energies for corner and edge shared MoO4 moiety favoured the formation of the former one. Calculated HOMO-LUMO electronic transition for tetrahedrally coordinated molybdenum in Mo-containing ring clusters showed a shift of 15 nm from that in Mo-containing linear chain clusters. These results were compared with the experimental results obtained from UV-DRS studies on Mo-MCM-41 catalyst.