Active Sites in Supported Single-Site Catalysts: An NMR Perspective

Development of well-defined heterogeneous catalysts requires detailed structural characterization of active sites, an essential step toward establishing structure-activity relationships and promoting rational designs of catalysts. Solid-state NMR has emerged as a powerful approach to provide key molecular-level information about active-site structures and dynamics in heterogeneous catalysis. Here, we describe how one can apply solid-state NMR, ranging from 1D chemical shift assignments (and additional parameters, C_Q and η, for quadrupolar nuclei, I > ¹/₂) to 2D correlations, to analysis of chemical shift anisotropy, providing unprecedented structural information about a broad range of materials. We also describe how modern hyperpolarization techniques like dynamic nuclear polarization can be used to improve the sensitivity of NMR, and make various challenging 1D/2D NMR experiments feasible, thus paving the way to determine the structures of surface sites.