Synergistically Modulating the Active-Site Density and Charge-Transfer in Covalent Organic Frameworks for Boosting Electrocatalytic Water Splitting

Abstract

Covalent organic frameworks (COFs) have emerged as a promising precise platform for designing metal-free bifunctional electrocatalysts. Herein, we designed and synthesized two bicarbazole-based metal-free COFs (NUST-69 and NUST-70) with different organic linkers, where NUST-70 incorporates a benzothiadiazole (BT) moiety. Notably, NUST-70, featuring multiple N and S active sites of BT and a donor-acceptor (D-A) structure, demonstrates exceptional electrocatalytic activity, particularly for oxygen evolution reaction (OER), achieving an overpotential of 292 mV at 10 mA cm -2 and maintaining stability over 48 h of chronoamperometry testing. The enhanced OER performance is attributed to the synergistically modulating the active-site density and charge-transfer induced by the BT unit, as confirmed by experimental characterization and theoretical calculations. This study highlights the potential of rationally designed D-A type COFs as high-performance metal-free electrocatalysts for advancing clean energy conversion.