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

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.