Efficient and selective oxidation of cyclohexane to cyclohexanone over flake hexagonal boron nitride/titanium dioxide hybrid photocatalysts

Selective oxidation of cyclohexane (CHA) with oxygen (O2) to product cyclohexanone (CHA-one) is an important reaction for the modern chemical industry. The present work constructs a flake hexagonal boron nitride/titanium dioxide (h-BN/TiO2) hybrid photocatalyst to achieve a desired selective and efficient oxidation of CHA to form CHA-one with a mild and green condition under atmospheric pressure, at room temperature, and in solvent-free. The activity of 14 wt% h-BN/TiO2 composite is significantly enhanced to about four times as compared with that of bare TiO2. Moreover, the CHA-one selectivity of 14 wt% h-BN/TiO2 composite (>85%) is much higher than that of pure TiO2 (approximately 60%). Additionally, h-BN/TiO2 composites can also display superior cycling stability and recoverability. The reasons for the promoted photocatalytic performance of h-BN/TiO2 were revealed by the photo-electrochemical experiments and DFT calculations. Both the negatively charged h-BN and its flake structure can effectively enhance valence band holes transfer from the inside of TiO2 to h-BN surface, and further improve the separation of photoformed hole-electron pairs to promote photocatalytic performance. The present approach will contribute to the build of more efficient photo-oxidation systems and to the construction of advanced composite photocatalysts for selective oxidation.