Defect-engineered Zr-MOFs with enhanced O2 adsorption and activation for photocatalytic H2O2 synthesis

Abstract

Defect engineering has recently received much attention as an effective approach for improving photocatalytic performances. Herein, UiO-66-NH₂ with missing ligand defects (DUiO-66-NH₂) wrapped by ZnIn₂S₄ was investigated for photocatalytic H₂O₂ production under visible light. The defects in DUiO-66-NH₂ enable efficient charge separation and O₂ capture, which are the key factors in accelerating H₂O₂ production. Specifically, the O₂ adsorption capacity over ZnIn₂S₄/DUiO-66-NH₂ was improved by a factor of 3.1 as compared to its counterpart without defects. As a result, in ambient air and pure water without any sacrificial agents, the H₂O₂ yield of ZnIn₂S₄/DUiO-66-NH₂ was 340 μmol L⁻¹, which was significantly higher than that of ZnIn₂S₄/UiO-66-NH₂ (150 μmol L⁻¹). The main H₂O₂ formation pathway over ZnIn₂S₄/DUiO-66-NH₂ is an indirect oxygen reduction reaction with ·O₂⁻ as the intermediate, and the defects in UiO-66-NH₂ could act as active sites to adsorb and activate O₂ to produce ·O₂⁻. However, the H₂O₂ generation over ZnIn₂S₄/UiO-66-NH₂ undergoes both indirect and direct oxygen reduction reactions. This work could provide new insights and inspire further research into defect engineering of MOFs and photocatalytic H₂O₂ synthesis.