Metal-free redox active covalent organic frameworks for electrocatalytic oxygen reduction reaction.

Designing efficient, metal-free covalent organic framework (COF) electrocatalysts is a promising strategy for the oxygen reduction reaction (ORR) due to their structural tunability and stability. Herein, we report two redox-active donor-acceptor COFs, TAPA-DHTD and TTT-DHTD, incorporating a thiophene-based dithiophenedione (DHTD) unit. Among them, TTT-DHTD exhibits superior ORR performance with a half-wave potential (E1/2) of 0.82 V vs RHE, approaching that of 20% Pt/C (0.85 V) and surpassing most reported metal-free COFs. It also demonstrates excellent methanol tolerance and long-term durability, maintaining activity over 120 hours. Density functional theory (DFT) calculations reveal that the donor-acceptor framework optimizes the p-band center, enhances charge separation, and improves adsorption of oxygenated intermediates, thereby accelerating ORR kinetics. This work provides a rational strategy for designing durable, high-performance metal-free electrocatalysts for sustainable energy applications.