Linkage-engineered covalent organic frameworks regulating the electron transfer for promoting oxygen reduction

Abstract

Covalent organic frameworks (COFs) play a crucial role in metal-free electrocatalysts for promoting oxygen reduction reaction (ORR) due to their adjustable skeleton structure and catalytic activity. While it is true that numerous studies have explored COFs for ORR, the critical gap by providing a systematic framework for ligand-driven electronic state manipulation is essential for designing highly active COF-based ORR catalysts. Herein, a series of COF-based metal-free materials have been conceived and synthesized by linkage-engineered strategy with dicarboxaldehyde (BPC), bipyridine-dicarbaldehyde (BPA) and benzodithiophene (BDA) as electronic linkages. Consequently, by incorporating different linkages into COFs, the surface area, electronic state, hydrophobic properties and affinities towards intermediates are optimized. Notably, the benzodithiophene-linked COF (denoted as BDA-COF) has greater catalytic ability with a half-wave potential of 0.74 V vs. RHE and an onset potential of 0.86 V vs. RHE than dicarboxaldehyde (denoted as BPC-COF) and dicarbaldehyde (denoted as BPA-COF). Relevant characterizations, in situ techniques and theoretical calculations confirm that thiophene-S-based COF promotes the electronic migration and enhances the interaction with the intermediate. The result provides insight into for illustration of a high-performance COF-based electrocatalyst via a linkage-engineered approach.