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.