Charge-Delocalizing sp-Hybridized COFs for Selective H2O2 Electrosynthesis.

Abstract

Hydrogen peroxide (H₂O₂) is an important oxidant for chemical manufacturing, environmental remediation, and biomedical applications, yet its industrial production still relies mainly on the energy-intensive anthraquinone process. Electrochemical H₂O₂ synthesis via the two-electron oxygen reduction reaction (2e^- ORR) provides a sustainable alternative but is often hindered by sluggish charge transport and insufficient O₂ activation. Here, we develop a bond-hybridization strategy by incorporating sp-hybridized acetylene units into the vertex or linker of covalent organic frameworks (COFs). The resulting COFs feature extended π-conjugation, enhanced charge delocalization, and electronically polarized pores, thereby strengthening O₂ adsorption and activation. Compared with sp²-dominated analogues, these sp-hybridized COFs show faster charge-transfer kinetics, higher H₂O₂ selectivity, and improved 2e^- ORR activity. In a flow cell, the optimized catalyst delivers an H₂O₂ production rate of 27.8 mol g^-1 h^-1 and a peak Faradaic efficiency of 91.7% at 150 mA cm^-2. Mechanistic analyses combining electronic-structure calculations and in situ vibrational spectroscopy reveal that sp hybridization reshapes frontier-orbital distributions and local charge density, thereby coupling framework-wide charge delocalization with favorable O₂ adsorption and *OOH stabilization. These results establish bond hybridization as a molecular-level design parameter for catalytic selectivity in COFs, extending framework engineering beyond conventional functional-group and building-block modification.