Understanding photocatalytic hydrogen peroxide production in pure water for benzothiadiazole-based covalent organic frameworks

Abstract

Photocatalytic production of hydrogen peroxide (H₂O₂) presents a promising and sustainable alternative to the current industrial anthraquinone route. Recent years have witnessed the emergence of covalent organic frameworks (COFs) as excellent photocatalysts, owing to their tunable band gaps, structural versatility and functional tunability. However, the current activity of COFs is limited and often relies on sacrificial agents to scavenge the holes in the photo-excited COFs. In this study, we introduce two benzothiadiazole-based COFs with tunable electronic structures and electron affinities for photocatalytic H₂O₂ production. The triazine-containing material, TAPT-BT-COF, exhibits outstanding charge separation and achieves a H₂O₂ production rate of 1360 ± 30 μmol h⁻¹ g_cat⁻¹ in pure water, nearly twice as high as the benzene-containing TAPB-BT-COF (730 ± 30 μmol h⁻¹ g_cat⁻¹). Moreover, TAPT-BT-COF demonstrates a remarkable apparent quantum efficiency of 4.9% at 420 nm. This study underscores the significance of framework conjugation and provides valuable insights for the design of advanced photocatalytic framework materials with efficient charge separation.