Tailoring Multiple Coordination Environments of Cobalt-Only Ladder Organic Framework for Bifunctional Oxygen Electrocatalysis.

Developing efficient oxygen electrocatalysts is crucial for the progress of future energy conversion and storage systems. Herein, a fully conjugated ladder organic framework is designed with densely populated cobalt sites (HATN-BiSalphen@KB). The molecular characteristics of the catalytic sites provide a trustworthy model for investigating the oxygen catalysis mechanism. Theoretical calculations combined with in situ ATR-FTIR spectroscopy demonstrate that the electronic interaction of the Co2N4O2 and CoN2Cl2 sites shifts the d-band center of Co atoms, optimizing oxygen intermediate adsorption/desorption energetics and boosting bifunctional catalytic performance. Consequently, the catalyst exhibits exceptional bifunctional activity, achieving a remarkable oxygen reduction reaction (ORR) half-wave potential of 0.983 V alongside a low oxygen evolution reaction (OER) overpotential of 310 mV at 10 mA cm-2. In addition, the assembled rechargeable zinc-air batteries demonstrate a high peak power density of 254.1 mW cm-2 and outstanding charge-discharge cycling stability for 450 h. This work provides valuable insights into designing advanced bifunctional oxygen electrocatalysts through atomic-level modulation of the coordination environment.