English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

The dispersion and coordination of aluminium species on the surface ofsilica-alumina based materials are essential for controlling their catalyticactivity and selectivity. Al(IV) and Al(VI) are two common coordinations of Alspecies in the silica network and alumina phase, respectively. Al(V) is rare innature and was found hitherto only in the alumina phase or interfacescontaining alumina, a behavior which negatively affects the dispersion,population, and accessibility of Al(V) species on the silica-alumina surface.This constraint has limited the development of silica-alumina based catalysts,particularly because Al(V) had been confirmed to act as a highly active centerfor acid reactions and single-atom catalysts. Here, we report the directobservation of high population of homogenously dispersed Al(V) species inamorphous silica-alumina in the absence of any bulk alumina phase, by highresolution TEM/EDX and high magnetic-field MAS NMR. Solid-state 27Almulti-quantum MAS NMR experiments prove unambiguously that most of the Al(V)species formed independently from the alumina phase and are accessible on thesurface for guest molecules. These species are mainly transferred to Al(VI)species with partial formation of Al(IV) species after adsorption of water. TheNMR chemical shifts and their coordination transformation with and withoutwater adsorption are matching that obtained in DFT calculations of thepredicted clusters. The discovery presented in this study not only providesfundamental knowledge of the nature of aluminum coordination, but also pavesthe way for developing highly efficient catalysts.

Discovery of homogeneously dispersed pentacoordinated Al(V) species on the surface of amorphous silica-alumina