Novel three-dimensional covalent organic framework hybrid catalysts with atomically dispersed FeN4 sites for highly efficient oxygen reduction reaction†

To date, various nonprecious metal catalysts have been developed for the oxygen reduction reaction (ORR). A common synthetic strategy for preparing catalysts is pyrolysis preparation; however, high-temperature pyrolysis may destroy the original structure of the catalyst, making the electrocatalytically active sites uncertain. In this paper, we utilized a pyrolysis-free method to successfully construct a novel three-dimensional (3D) covalent organic framework (COF) hybrid catalyst (Fe-3DCOF/CNT) with atomically dispersed FeN₄ sites. Compared to two-dimensional (2D) COFs, 3D COFs are considered to have highly accessible surface area and well-exposed active sites along with interconnected nano-channels, which are more conducive to the catalysis of the ORR. As expected, Fe-3DCOF/CNT exhibited impressive ORR catalytic activity (E_1/2 = 0.921 V, J_L = 5.714 mA cm⁻²). Besides, the stability and methanol tolerance of Fe-3DCOF/CNT were far beyond those of 20% Pt/C. This work discloses the broad prospect of electrocatalysts based on 3D COFs with well-defined active sites by pyrolysis-free synthesis.