Post-synthetic Mechanochemical Incorporation of Al-Species into the Framework of Porous Materials: Toward More Sustainable Redox Chemistries

The mechanochemical incorporation of catalytically active Al species in low loadings was successfully accomplished into the framework of mesoporous silica (SBA-15 and MCM-41) materials using a simple wet milling approach (with aluminum isopropoxide as source of aluminum) and a dry milling approach (using low quantities of Al-containing MOF materials). Characterization data pointed to the successful incorporation of Al species (typically with loadings of ca. 0.2-0.4 wt %) that were mostly tetrahedrically coordinated. Despite such extremely low loadings, the isolated aluminum oxide species exhibited promising activities and stability in selective mild oxidations under various conditions (microwave irradiation and mechanochemistry), including the selective oxidation of benzyl alcohol to benzaldehyde, isoeugenol to vanillin, and diphenyl sulfide to diphenyl sulfoxide, as compared to similarly synthesized impregnated catalysts.