Modulating Core Polarity in Metal-free Covalent Organic Frameworks for Selective Electrocatalytic Hydrogen Peroxide Production.

Tuning the charge density at the active site to balance the adsorption ability and reactivity of oxygen is extremely significant for driving a two-electron oxygen reduction reaction (ORR) to produce hydrogen peroxide (HO). Herein, we have highlighted the influence of intermolecular polarity in covalent organic frameworks (COFs) on the efficiency and selectivity of electrochemical HO production. Different C3 symmetric building blocks have been utilized to regulate the charge density at the active sites. The benzene-cored COF, which exhibits reduced polarity than the triazine-cored COF, displayed enhanced performance in HO production, achieving 93.1 % selectivity for HO at 0.4 V with almost two-electron transfer and a faradaic efficiency of 90.5 %. In-situ electrochemical Raman spectroscopy and scanning electrochemical microscopy (SECM) were employed to confirm HO generation and analyze spatial reactivity patterns. These techniques provided detailed insights into localized catalytic behavior, emphasizing the influence of core polarity.