Tuning Electrochemical Properties of Metal-Free Covalent Organic Frameworks Through Hydrogen-Bonding Interactions

Abstract

Accurately identifying and enhancing catalytic activity in metal-free, carbon-based electrocatalysts remains a fundamental challenge, largely due to the difficulty of concurrently optimizing hydrophilicity and oxygen affinity at active sites. Herein, a hydrogen-bonding-driven strategy is presented to boost oxygen reduction reaction (ORR) performance in covalent organic frameworks (COFs). By integrating hydrazone linkages with alkoxy-functionalized pore walls, a hydrophilic skeleton capable of forming tunable intramolecular hydrogen-bonding networks is constructed. These interactions induce asymmetric electron distributions that enhance the simultaneous adsorption of water and oxygen molecules. Consequently, the hydrazone-linked COFs exhibit a half-wave potential of 0.78 V, outperforming all previously reported metal-free COF-based electrocatalysts. Density functional theory (DFT) calculations reveal that the improved activity originates from favorable *OOH and *OH adsorption energies at hydrogen-bonding centers, along with stabilized O2/H2O binding. This synergistic modulation of the local microenvironment-through hydrogen bonding and electronic structure engineering-affords enhanced activity, selectivity, and long-term durability. This work offers a rational design paradigm for advancing metal-free COF electrocatalysts toward sustainable energy conversion.