Synergic Regulation of Active Site Electron Polarization and Interlayer Electron Coupling in COFs for Photocatalytic Hydrogen Peroxide Synthesis.

Abstract

Covalent organic frameworks (COFs) are promising photocatalysts for the oxygen reduction reaction (ORR), yet reconciling the different electronic requirements in different elementary steps remains challenging. Herein, guided by the Sabatier principle and Marcus-Hush electron-transfer theory, we report a PyaD COF with dual electronic regulation targeting both atomic active sites and the molecular skeleton. Specifically, moderately polarized active sites balance the adsorption/desorption step by avoiding overly strong intermediate binding and reducing the H2O2 desorption barrier from 0.82 to 0.46 eV, while reinforced interlayer π-π electron coupling across the COF skeleton promotes electron transfer, prolonging the excited-state lifetime by more than one order of magnitude. The dual electronic regulation affords a sacrificial-agent-free H2O2 production rate of 4227.5 µmol g- 1 h- 1, which is approximately 4 times and 2.8 times higher than those of unregulated and singly regulated COFs, respectively. Furthermore, a membrane-based photo-enzyme cascade reactor system achieves selective hydroxylation of ethylbenzene to synthesize 1-phenylethanol, producing over 10 mmol gcat -1 L-1 within five irradiation cycles.