Theoretical and experimental insights into applicability of solid-state 93Nb NMR in catalysis

Ab initio DFT calculations of Nb-93 NMR parameters using the NMR-CASTEP code were performed for a series of over fifty individual niobates, and a good agreement has been found with experimental NMR parameters. New experimental and calculated Nb-93 NMR data were obtained for several compounds, AlNbO4, VNb9O25, K8Nb6O19 and Cs3NbO8, which are of particular interest for catalysis. Several interesting trends have been identified between Nb-93 NMR parameters and the specifics of niobium site environments in niobates. These trends may serve as useful guidelines in interpreting Nb-93 NMR spectra of complex niobium oxide systems, including amorphous samples and niobium-based multicomponent heterogeneous catalysts. Potential applications of Nb-93 NMR to study solid polyoxoniobates are discussed.