Mesoporous Aluminum Silicate Catalyst with Single-Type Active Sites: Characterization bySolid-State NMR and Studies of Reactivity for Claisen Rearrangement Reactions
A mesoporous aluminum silicate (Al-MS) material has been successfully synthesized via a base-catalyzedco-condensation reaction. Solid-state NMR studies showed that the aluminum atoms are tetrahedrallycoordinated and are stable up to at least 400 °C. The double resonance 27Al-29Si NMR experiment providedfirst 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 theoverall Si/Al ratio of 60. Reactivity study of the mesoporous aluminosilicate shows an excellent catalyticreactivity for the Claisen rearrangement of allyl phenyl ether despite the low surface concentration of Al.