Monomolecular VB2-doped MOFs for photocatalytic oxidation with enhanced stability, recyclability and selectivity†
Monomolecular VB2 (vitamin B2) was doped into UiO-66 [Zr6O4(OH)4(BDC)12, BDC = 1,4-benzenedicarboxylic acid] via chemical bonds and the obtained VB2@UiO-66 could be used as a heterogeneous photocatalyst. The coordination with UiO-66 was found to be able to positively shift the conduction band of VB2, which thermodynamically precluded the formation of other reactive oxygen species (like O2˙−) except 1O2 under visible light irradiation and led to 1O2 as the only reactive oxygen species for VB2@UiO-66. This result was totally different from that for VB2, which produced various reactive oxygen species, such as O2˙− and 1O2. Due to the fact that 1O2 was the only reactive oxygen species, VB2@UiO-66 displayed excellent photocatalytic selectivity (∼100%) towards benzyl alcohol oxidation. At the same time, chemical bonding with UiO-66 greatly improved the stability of VB2 under visible light. After 5 cycles, the conversion was still 91% and the selectivity was close to 100%. This work offers not only a solution to the poor recyclability, stability and selectivity of VB2 as a photocatalyst but also a new efficient strategy to extend the photocatalytic applications of MOFs by immobilizing common biological antioxidants on their particular sites.