Heteroatom-induced band-reconstruction of metal vanadates for photocatalytic cyclohexane oxidation towards KA-oil selectivity

Abstract Structure-function correlation constitutes a central theme in the selective photocatalytic oxidation of cyclohexane with molecular oxygen, as a result of precise tailoring band-structure towards KA-oil selectivity. Herein, we comparatively and systematically investigate the correlation among optical properties, electronic structure, and photocatalytic performance of two d°-vanadate photocatalysts (BiVO 4 and Cu 3 V 2 O 8 ) using theoretical calculations and experimental techniques. Results show that BiVO 4 promotes the selective oxidation pathway under visible-light irradiation with higher efficiency (TOF = 7.5 h −1 , based on the molar amount of V sites) and chemoselectivity (cyclohexanone/cyclohexanol molar ratio = 3.0) than the Cu 3 V 2 O 8 . Meanwhile, the photocatalytic performance of BiVO 4 demonstrates high photocatalytic selectivity towards KA-oil (95%), while Cu 3 V 2 O 8 seems to facilitate the accommodation of chlorine promoters, leading to very different chlorocyclohexane selectivity (46%). Such the distinct photocatalytic performances of BiVO 4 and Cu 3 V 2 O 8 can be ascribed to their unique electronic structures to facilitate the e − −h + charge carriers and generation of reactive species during photoirradiation. The Bi 3+ 6p states of BiVO 4 are predominant components of the conduction band minimum (CBM) and hybridize with Bi 3+ 6 s , and O 2− 2p and V 5+ 3d orbitals at the valence band maximum (VBM); whereas the Cu 2+ 3d and V 5+ 3d orbitals contribute to the CBM of Cu 3 V 2 O 8 , and Cu 2+ 3d , O 2− 2p and V 5+ 3d orbitals at the VBM. So BiVO 4 with s − p matrix elements is more effective than the Cu 3 V 2 O 8 in producing OH, h + and H 2 O 2 , which can rapidly oxidize the C − Cl band cleavage for chlorocyclohexane intermediate to regenerate newly Cl radicals in the next cycle reactions. Heteroatom-tuning of photocatalytic performance is further supported by universal evidences from experimental results by replacing Bi or Cu of the above vanadates with Ag, La, Sr, Fe or Ti atom and the study of the electrons, holes and radicals mediated reaction pathway by scavengers, respectively.