Abstract:

The oxygen reduction reaction is the core electrochemical process for energy storage. Because of its slow kinetic rate， it is urgent to prepare electrocatalysts with high activity to promote the rate of this reaction. The π-π stacking structure of two-dimensional covalent organic frameworks （2D COFs） can endow the framework with high conductivity， and the one-dimensional ordered pores are beneficial to promote the transport of intermediate reactants. Therefore， it has good application prospects in the field of renewable energy and serves as a powerful catalytic platform for energy storage and conversion. Herein， we successfully prepare two 2D COFs （JUC-600 and JUC-601） by introducing metalloporphyrin and thioethers units into 2D COFs. The results suggest that two COFs have AA stacked sql topology. Electrochemical tests show that the Co²⁺ coordinated JUC-601 has a higher starting potential （0.825 V） and half-wave potential （0.7 V）， a larger active surface area （7.8 mF/cm²）， and a lower Tafel slope （58 mV/dec）. We believe that this is due to the high specific surface area and high porosity of JUC-601， which makes the intermediate products easier to contact and transport on the surface and pores of COFs. In addition， the presence of Co²⁺-porphyrin units and thioether units changes the electronic structure of the entire skeleton， which is more conducive to electron transfer. This work not only develops new 2D porphyrin-thioether-based COF materials， but also expands the application of COFs in the field of electrocatalysis.

Key words: Covalent organic framework, Metalloporphyrin unit, Thioether, ORR electrocatalyst