Electronic Modulation of Flexible Ether Oxygen-Based Covalent Organic Frameworks for Efficient Oxygen Reduction...

Ether oxygen-based covalent organic frameworks (EO-COFs) with intrinsic flexibility characteristics hold promise for applications in emerging electrochemical energy conversion technologies due to the adaptable pore microenvironments. However, achieving efficient oxygen reduction reaction (ORR) requires not only accessible pores but also facilitated charge transfer from the electrode to catalytically active sites within the extended framework and the simultaneous optimization of these two coupled processes remains challenging. Here, we synthesized two new EO-COFs and incorporated electron-withdrawing triazine units to enhance charge-transfer capability and modulate the electronic states, thereby improving their metal-free ORR activity. Moreover, the ether-oxygen moieties contribute to the formation of a more adaptive pore microenvironment and facilitate mass transport. Notably, the optimized THD-TOT-COF exhibits a high half-wave potential of 0.77 V and a turnover frequency value of 0.0021 s^-1. Combined theoretical calculations and in-situ spectroscopy analyses reveal that the enhanced catalytic activity originates from the facilitated formation of the *OOH and *OH intermediates on carbon atoms within the triazine ring of THD-TOT-COF. This work provides a rational strategy for designing metal-free COFs electrocatalysts by coupling electronic-state modulation with a flexible ether-oxygen-containing framework microenvironment.