We analyzed the X-ray absorption fine structure (XAFS) spectra of W L1- and L3-edges in order to determine the structure of various W species on TiO2. Two 2p → 5d transitions were observed in the second derivative of the W L3-edge X-ray absorption near-edge structure (XANES) spectra of all samples containing W (WO3, Na2WO4, Cr2WO6, Ba2NiWO6, (NH4)10W12O41·5H2O, Sc2W3O12, H3PW12O40·13H2O, and TiO2-loaded WO3 samples). These two transitions can be assigned to 5d orbitals split by the ligand field. The split in the 5d orbital has a linear relationship with the area of pre-edge peak of the W L1-edge XANES spectrum. This linear relationship is supported by density functional theory (DFT) calculations of the octahedral and tetrahedral W models. On the basis of this linear relationship, we estimated the structure of various W species on TiO2. The obtained structure is in accordance with the curve fitting analysis of W L3-edge extended X-ray absorption fine structure (EXAFS). Additionally, we found that the octahedral WO3 species loaded on TiO2 sample exhibits the high activity for the photo-oxidation of NH3 (photo-SCO).

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b S Supporting Information O xidation of amine to imine is an important chemical transformation because of the versatile applications of imines as synthetic intermediates of medicines or biologically active nitrogen containing organic compounds. 1 Several oxidation procedures using stoichiometric oxidants such as 2-iodoxybenzoic acid 2,3 or N-tert-butylphenylsulfinimidoyl chloride 4 have been reported. However, a catalytic system using molecular oxygen as a sole oxidant has been desired in view of green chemistry. 5,6 In this context, a number of transition-metal catalyzed aerobic oxidation systems have been developed. Ru-based catalysts such as RuCl 3 , 7 [RuCl 2 (RCH 2 NH 2 ) 2 (PPh 3 ) 2 ], 8,9 Ru-porphyrin, 10 Ru-hydroxyapatite, 11 Ru 2 (OAc) 4 Cl, 12 and Ru/Al 2 O 3 13 are known to be effective for aerobic oxidation of amines. Au nanoparticles supported on Al 2 O 3 , 14,15 CeO 2 , 14,15 graphite, 16 and hydroxyapatite 16 are also found to be good catalysts for amine oxidation. But in these systems, expensive precious metals are employed and relative high temperature (mostly >373 K) is required.Utilizing semiconductor photocatalysts for aerobic oxidation of organic molecules has practical advantages of economical efficiency, environmental-friendliness, reusability, and durability. In addition, to effectively utilize solar energy, it is necessary to develop a material that will function under visible light. 17 Very recently, Su and co-workers reported that mesoporous graphite carbon nitride (mpg-C 3 N 4 ) can work as effective photocatalyst to activate O 2 for the selective oxidations of benzylic alcohols and amines with visible light. 18,19 Although this material exhibits excellent catalytic performance under visible light irradiation, high oxygen pressure (0.5 MPa) and trifluorotoluene as solvent are necessary to obtain good yields. Zhao et al. reported that photooxidation of amines using TiO 2 with UV light gave a high selectivity to imines under a diluted condition. 20 We recently reported that photocatalytic oxidation of various alcohols proceeded selectively over niobium oxide (Nb 2 O 5 ) under a mild condition. 21,22 Nb 2 O 5 showed higher selectivities to partial oxidation products; therefore, it can be thought that Nb 2 O 5 is more suitable for selective oxidation than TiO 2 . Moreover, we found that Nb 2 O 5 can catalyze the selective photooxidation of alcohols even under visible light

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