Directional Concerted Proton-Electron Transfer in COFs for Efficient Photocatalytic H₂O₂ Production.

Abstract

Photocatalytic two-electron oxygen reduction reaction (2e^- ORR) offers a sustainable route for green H₂O₂ synthesis. However, its efficiency is fundamentally constrained by the kinetic mismatch between proton transfer and electron migration across heterogeneous interfaces. Inspired by concerted proton-electron translocation in natural hydrogenases, we report a catechol-triazine donor-acceptor (D-A) covalent organic framework, 2,3-Dhta-Tt, for directional concerted proton-electron transfer (DCPET) during photocatalytic H₂O₂ production. The intrinsic built-in electric field, combined with a catechol-derived dynamic proton-relay network, aligns proton and electron fluxes and establishes a periodic co-transport channel toward triazine acceptor sites. At the molecular level, the catechol donor units dominate the highest occupied molecular orbital (HOMO), acting simultaneously as photoexcitation centers and initial proton-release sites, thereby synchronizing proton delivery with electron migration. This vectorial coupling lowers the activation barrier for O─O hydrogenation and promotes highly selective 2e^- ORR, affording an H₂O₂ production rate of 27.22 mmol g^-1 h^-1 in pure water. The framework also exhibits proton conductivity of 6.09 × 10^-5 S cm^-1 and an extended excited-state lifetime of 94.45 ps. Isotope labeling, operando spectroscopy, and DFT calculations support a proton-cycling process and directional proton/electron participation. This work advances heterogeneous photocatalyst design beyond conventional PCET cooperativity.