MOF-Derived Oxygen-Vacancy-Rich ZrO₂/UiO-66-NH₂ for Efficient Visible-Light-Driven Oxidation of Benzyl Alcohol

Abstract

The development of efficient photocatalysts for selective organic transformations under visible light remains a major challenge in sustainable chemistry. In this study, we present a straightforward solvothermal strategy for fabricating a defect-engineered ZrO₂/UiO-66-NH₂ hybrid material with abundant oxygen vacancies, enabling the visible-light-driven oxidation of benzyl alcohol to benzaldehyde. By optimizing the solvothermal treatment duration, the composite (UiO-66-NH₂-2 h) achieves a 74.1% conversion of benzyl alcohol with > 99% selectivity toward benzaldehyde under mild conditions, substantially outperforming pristine UiO-66-NH₂. Structural and mechanistic studies reveal that the solvothermal process induces the in situ formation of ultrasmall, uniformly dispersed ZrO₂ nanoparticles (~ 2.3 nm) within the MOF matrix, while simultaneously generating abundant oxygen vacancies, as confirmed by XPS, EPR, and HRTEM analyses. The defect-mediated electronic structure of the ZrO₂/UiO-66-NH₂ hybrid enhances visible-light absorption, facilitates charge carrier separation, and promotes efficient activation of O₂ into superoxide radicals (·O₂⁻), the primary reactive species. Transient photocurrent measurements and electrochemical impedance spectroscopy further verify the improved charge separation efficiency. The synergistic interplay between oxygen vacancies and the intimate ZrO₂/UiO-66-NH₂ interface provides a unique defect-mediated charge transfer pathway, distinguishing this system from conventional heterojunctions. This study demonstrates a facile, one-step approach to integrate defect engineering with interfacial hybridization in MOF-based photocatalysts, offering a scalable route for solar-driven organic synthesis.

Keywords

Visible-light photocatalysis / Benzyl alcohol oxidation / Oxygen vacancy / Heterostructure / UiO-66-NH₂

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