Fully-Conjugated Covalent Organic Frameworks with Two Metal Sites for Oxygen Electrocatalysis and Zn-Air Battery

Covalent organic frameworks (COFs) are a promising alternative toward catalysis, due to the unique framework structure and the excellent chemical stability. However, the scarcity of unsaturated metal sites and the low conductivity have constrained the advancement of these materials for catalysis of electrochemical reactions. Exploring next-generation conductive metal-covalent organic frameworks (M-COFs) with extra metal active sites is crucial for improving their catalytic activity. Herein, a novel fully-conjugated M-COFs (Co-PorBpy-Co) with two types of metal sites is proposed and achieved by solvothermal method in the presence of carbon nanotube (CNT). The electrocatalyst constructed by the Co-PorBpy-Co exhibits excellent oxygen reduction reaction (ORR) activity (E-1/2 = 0.84 V vs RHE, n = 3.86), superior to most COFs-based catalysts. Theoretical result shows the Co-N-2 sites are extremely active for ORR, and Co-PorBpy-Co exhibits excellent conductivity for electron transfer. The Zn-air battery constructed by Co-PorBpy-Co/CNT manifests excellent power density (159.4 mW cm(-2)) and great cycling stability, surpassing that of 20 wt% Pt/C catalyst. This work not only proposes a novel design concept for electrocatalysts, but establishes a mechanism platform for single-metal atom electrocatalysis and synergistic effect.

Automated summary

In this research, a novel conductive metal-covalent organic framework (M-COFs) with two types of metal active sites was synthesized using a solvothermal method. The M-COFs showed excellent catalytic activity in the oxygen reduction reaction (ORR) and exhibited superior conductivity for electron transfer. The constructed Zn-air battery using M-COFs demonstrated high power density and great cycling stability, surpassing the performance of a commonly used platinum-based catalyst. This work not only presents a novel design concept for electrocatalysts, but also establishes a mechanism platform for single-metal atom electrocatalysis and synergistic effect.