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

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.