Enhanced Photocatalytic H₂O₂ Production on Terpyridine-Based Acrylonitrile-Linked Covalent Organic Frameworks with Asymmetric Localized Electron Distribution.

Abstract

Covalent organic frameworks (COFs) serve as promising photocatalysts for sustainable photosynthesis of H₂O₂ from water and air due to their well-defined architecture and precisely controllable structure. The key to achieving high H₂O₂ production rates lies in the efficient adsorption of O₂ and effective charge transfer over COFs. In this work, we have studied a terpyridine-based acrylonitrile-linked COF (TPy-acr COF) with optimum localized electron distribution and enhanced charge transfer for two-electron transfer oxygen reduction toward H₂O₂ production. The electron-deficient pyridine nitrogen atoms in the terpyridine unit induce an asymmetric electron distribution with localized electron density at the adjacent carbon atoms, while the electron-withdrawing acrylonitrile linkage increases the electron distribution asymmetry of the entire framework. Consequently, the high electron-density carbon atoms in the terpyridine units of TPy-acr COF show strong binding for O₂ and fast charge transfer to the key intermediate ^*OOH. Remarkably, the TPy-acr COF enabled a high production rate of 4.85 mmol g^-1 h^-1 for H₂O₂ directly from water and air. An outdoor scale-up experiment shows an average H₂O₂ production rate of 1.14 mmol g^-1 h^-1 over TPy-acr COF using water in ambient air under natural sunlight, demonstrating practical application potential with sustainability, simplicity, and scalability.