Ni-Modified Defect-Engineered NH₂-UiO-66 for Efficient H₂O₂ Photosynthesis Coupled with Benzyl Alcohol Oxidation

Photocatalytic H₂O₂ production coupled with selective organic oxidation provides a promising strategy for simultaneously generating value-added oxidants and chemicals under mild conditions. Herein, Ni-modified defect-engineered NH₂-UiO-66 photocatalysts (Ni/UN) are constructed by introducing Ni species into a vacuum-treated NH₂-UiO-66 framework (UN). Compared with the original NH₂-UiO-66 and the defect-treated UN, Ni/UN exhibits weakened photoluminescence emission, enhanced transient photocurrent response, and reduced electrochemical impedance, indicating that the separation and transfer of photogenerated charge carriers have been improved. The band structure analysis further reveals that Ni/UN has a narrow band gap of approximately 2.52 electron volts and a slightly more negative conduction band position (-0.50 V), which is conducive to the photoinduced reduction reaction. The importance of O₂ in the photocatalytic process was demonstrated by changing the atmospheric conditions. Therefore, in the benzylalcohol system, under the oxygen atmosphere, Ni/UN achieved the highest H₂O₂ production rate of 3257 μmol g^-1 h^-1, accompanied by the continuous generation of benzaldehyde, with its content reaching 3420 μmol g^-1 after 60 min of irradiation. The scavenger experiment further indicates that photogenerated electrons and the active substances derived from oxygen are closely involved in the formation of H₂O₂, while the ·OH-related processes only play a limited contribution role. This study demonstrates an effective strategy for enhancing the performance of metal-organic framework (MOF)-based photocatalysts through defect engineering and metal coordination regulation, thereby achieving efficient photochemical production of hydrogen peroxide and the selective oxidation of benzyl alcohol.