Times Cited: 3 Article English Cited References Count: 61 556gq ; Ab initio periodic DFT calculations oil the structural and energy properties of different model niobium framework sites ill niobium-substituted zeolites containing sodalite cavities are presented and related to experimental FTIR measurements oil Nb containing SiBEA zeolite. The niobium framework sites are characterized by their calculated geometrical parameters, vibrational frequencies, and (de)protonation energies. Niobium(V) is stabilized ill the zeolite framework Lis a penta-coordinated site possessing one hydroxyl group. The Nb-OH group is not acidic. It Was found that hydration of this site was easier than dehydration, although the relative low hydrophylicity of the site. Dehydration of the site leads to the formation of Lewis acidic and Lewis basic sites as it was found in mesoporous niobium doped silica materials. These results are fully consistent with experimental data and allow the identification of the molecular structure of niobium sites in a zeolite framework.