Effect of the addition of propane and distortion of tetrahedral vanadium(V) species in VSiβ zeolites on the photodecomposition of NO

V_xSiβ catalysts with x=0.05, 0.2 and 1.75 V wt%, prepared by a two-step post-synthesis method, have been characterised by physical techniques and their photocatalytic reactivity investigated in the decomposition of NO. XRD and diffuse reflectance UV-Vis spectroscopy show that vanadium is incorporated as tetrahedral V^v species, a result confirmed by XANES and EXAFS. Photoluminescence spectra of V _x Siβ catalysts show well-resolved vibrational fine structures due to three different kinds of tetrahedral V^V (α, β, γ) species, with different degrees of distortion. Their relative amounts depend on V content and calcination/hydration treatments. Calcined-hydrated V_1.75Siβ, calcined V_1.75Siβ and calcined V_0.05Siβ exhibit mainly the α, γ and β kind of tetrahedral vanadium, respectively. These samples are active in the decomposition of NO under UV-irradiation, leading mainly to N₂ and O₂. The decomposition of NO is strongly enhanced in presence of propane, leading to higher yield of N₂. The latter strongly depends on the distortion of tetrahedral V species. The highest activity is found for the catalyst with tetrahedral V of highest distortion, lowest V=O bond length and biggest lifetime of its excited triplet state.