Classification and Identification of Facet- and Edge-Specific γ-Al 2 O 3 Surface Sites from 1 H/ 27 Al NMR Cross-Signatures and DFT Modeling

γ-Al2O3 is used as both a catalyst and a support for catalytic active phases. The properties of γ-Al2O3 have been ascribed to specific surface sites, with varying Al coordination number, acidity, and basicity, depending on the morphology of the material. Here, we combine surface-specific 27Al{1H} 2D high-field NMR (28.2T, 1.2 GHz for 1H frequency) at fast MAS (50 kHz) to observe four main distinct families of surface Al–OH sites. Comparing the measured NMR signatures (27Al δiso, CQ, and 1H δiso) to computed values from a large range of structural DFT models enables to identify specific edge and facet Al–OH surface sites in γ-Al2O3, including a distinct [4]Al–OH site with an unprecedented CQ approaching 18 MHz. This molecular-level description of alumina surfaces opens new opportunities to understand its unique properties, such as the stabilization of small particles down to single atoms, central to catalytic processes.