Unilateral Functionalization of Covalent Organic Frameworks: Local Electronic Modulation and Morphology-Enabled Mass Transport for Electrocatalytic Hydrogen Peroxide Production

Abstract

Abstract Achieving high selectivity and activity in the two-electron oxygen reduction reaction (2e– ORR) pathway critically depends on the synergistic modulation of a catalyst’s electronic structure and mass diffusion channels. This work proposes an asymmetric modulation strategy via unilateral functionalization, in which −CH3, −CN, −SO3H, and −NO2 moieties are incorporated into a series of covalent organic frameworks (COFs), systematically unraveling the multilevel regulatory mechanisms exerted by functional groups from molecular to macroscopic morphological scales. The research demonstrates that introducing strong electron-withdrawing −NO2 groups can effectively enhance charge transfer at adjacent carbon active sites, reduce the formation barrier of OOH* intermediates, and induce efficient 2e– ORR activity. Concurrently, the polarity and steric effects of functional groups induce structural evolution in COFs from spherical, rod-like to spiderweb-like architectures, wherein the interconnected network of COF-NO2 substantially enhances the diffusion efficiency of reactants and products. This synergy between electronic structure and macroscopic morphology enables COF-NO2 to achieve 94% H2O2 selectivity and a high production rate of 10.5 mol gcat–1 h–1 with sustained stability. This work not only provides outstanding catalysts for efficient electrochemical H2O2 synthesis but also clarifies functional group-induced electronic and morphological modulation, offering a novel paradigm for the rational design of porous catalytic materials.