Structure, Location, and Spatial Proximities of Hydroxyls on γ-Alumina Crystallites by High-Resolution Solid-State NMR and DFT Modeling: Why Edges Hold the Key

The atomic-scale characterization of surface active sites on γ-alumina still represents a great challenge for numerous catalytic applications. Here, we combine advanced density functional theory (DFT) calculations with one- and two-dimensional proton solid-state NMR experiments to identify the exact location spatial proximity hydroxyl groups crystallites. Our approach relies revisited models (100), (111), basal (110)b, lateral (110)l facets γ-alumina, as well edges at their intersections. Notably, show that ≃0 ppm AlTd-μ1-OH protons are predominantly located edges, where these free from H-bond network. proximities among μ2-OH revealed by 1H–1H dipolar correlation analyzed in light DFT calculations, which (110)b facet (110)b/(100) (110)b/(110)l edges. Using chlorine atoms probe presence hydroxyls, chlorination occurs selectively exchanging μ1-OH facets. By contrast, (111) not probed Cl. This exchange explains disappearance peak correlations involving species. Moreover, after chlorination, deshielding AlTd is observed high-resolution 27Al spectra. More subtle effects visible spectra, attributed disruption network course chlorination.