Proton-Detected Multidimensional Solid-State NMR Enables Precise Characterization of Vanadium Surface Species at Natural Abundance

Heterogeneous catalysts fulfill vital roles in industrial process, however due to the nature of the catalytic surfaces typically containing either a low abundance of active sites and being amorphous in nature leads difficulties when attempting to study the structure of the active sites. In this work we show how making use of fast MAS ssNMR probes allows to efficiently detect well resolved ¹H detected spectra of heterogeneous catalysts. This approach was applied to study the structure of surface species resulting from the grafting of VO(OiPr)₃ onto a partially dehydroxylated silica using the surface organometallic chemistry approach. The use of the ¹H sensitivity enabled to detect various hetero- and homo-nuclear correlation spectra in order to study the structure of this system and to resolve the structure of the grafted vanadium complex. More specifically, VO(OiPr)₃ grafts through both protonolysis and opening of siloxane bridges to generate a bis-grafted species, in contrast to most other alkoxides.