The growing pollution and energy crisis emphasize the need for the development of clean energy, such as fuel cells and metal-air batteries, in order to reduce the dependence on fossil fuels. In such clean energy devices, oxygen reduction reaction (ORR) is a key process in determining practical performance. Unfortunately it suffers from sluggish kinetics, resulting in large overpotentials and high efficiency penalties. To address this issue, rational design of non-precious metal catalysts with ORR performance comparable or even superior to precious metal is much needed.

Metal-organic frameworks (MOFs) are porous crystalline materials assembled from metal nodes and organic linkers. MOFs possess high surface areas, open metal sites, and tunable pore structures, and are therefore promising for ORR electrocatalysis, in pristine phases or as self-sacrificial templates (Fig. 1A). Besides MOFs, another class of metal-organic coordinated materials that are of great interest are metal-organic gels (MOGs). MOGs are viscoelastic solid-like materials assembled by metal-organic coordination in conjunction with other interactions. MOGs possess great inclusion properties, design flexibility and ease in synthesis, highlighting themselves as precursors for producing ORR electrocatalysts (Fig. 1A).

Herein, a series of MOFs/MOGs has been synthesized for ORR electrocatalysis. The catalytic ORR performance of the catalysts was evaluated through a rotating disk electrode technique, and the corresponding voltammograms are summarized in Fig. 1B. Several catalysts exhibit ORR activity comparable or greater than that of a commercial Pt/C benchmark, suggesting rational design approach of MOFs/MOGs offers a general solution for production of highly effective non-precious ORR electrocatalysts.