Identifying the Elusive Framework Niobium in NbS-1 Zeolite by UV Resonance Raman Spectroscopy

It was found that bands at 739, 963, and 1107 cm^-1 in the resonant Raman spectra are characteristics of framework penta-coordinated Nb^V -OH species, and that a band at 1336 cm^-1 in the UV Raman spectrum with excitation line at 320 nm is a sensitive detector for identifying extra-framework niobium species. The change of framework penta-coordinated Nb^V -OH species into Nb⁺ and NbO^- species due to dehydration was definitively confirmed based on UV resonance Raman and UV/Vis results.