Mesoporous Aluminum Silicate Catalyst with Single-Type Active Sites:  Characterization by Solid-State NMR and Studies of Reactivity for Claisen Rearrangement Reactions

A mesoporous aluminum silicate (Al-MS) material has been successfully synthesized via a base-catalyzed co-condensation reaction. Solid-state NMR studies showed that the aluminum atoms are tetrahedrally coordinated and are stable up to at least 400 °C. The double resonance 27 Al- 29 Si NMR experiment provided first direct evidence that all Al atoms are surrounded by Si atoms forming Al−O−Si bonds in the framework. The silicon to aluminum atomic ratio at the surface (Si/Al) s is estimated at around 100, which exceeds the overall Si/Al ratio of 60. Reactivity study of the mesoporous aluminosilicate shows an excellent catalytic reactivity for the Claisen rearrangement of allyl phenyl ether despite the low surface concentration of Al.