Selective two-electron oxygen reduction for H₂O₂ photosynthesis with anthraquinone-modified UiO-66/Zn₃In₂S₆ heterojunctions

Solar-driven artificial photosynthesis of hydrogen peroxide (H₂O₂) has emerged as a promising strategy for sustainable chemical production, yet its performance is often limited by rapid recombination of photogenerated charge carriers. Herein, an anthraquinone-modified UiO-66/Zn₃In₂S₆ (denoted as Zn₃In₂S₆/UiO-66-AQ) heterojunction is constructed to promote spatial separation of photogenerated charge carriers, thereby suppressing carrier recombination and enhancing H₂O₂ photosynthesis. The optimized photocatalyst achieves an H₂O₂ evolution rate of 4668 µmol g⁻¹ h⁻¹ in pure water without sacrificial agents, representing nearly a fourfold improvement over pristine Zn₃In₂S₆. Mechanistic investigations combining radical scavenging experiments and electron spin resonance (ESR) spectroscopy suggest that H₂O₂ generation predominantly proceeds through a photogenerated electron-driven two-electron oxygen reduction (2e⁻ ORR) pathway, with the superoxide radical (˙O₂⁻) acting as a key intermediate. In situ Fourier transform infrared spectroscopy further provides spectroscopic insights into the evolution of reaction intermediates during H₂O₂ formation. The catalyst also demonstrates stable performance over 8 cycles, and the generated H₂O₂ exhibits antibacterial activity against environmental Gram-negative bacteria. These results highlight the potential of Zn₃In₂S₆/UiO-66-AQ heterojunctions for solar-driven H₂O₂ photosynthesis and related environmental applications. This journal is © The Royal Society of Chemistry, 2026.