Dual-Metal-Site\nMetal–Organic Frameworks for\nOxygen Reduction: The Crucial Role of Environmental Species Covering\non the Secondary Site

Macrocycle-based dual-metal-site metal–organic\nframeworks\nemerge as promising catalysts whose activity can be conveniently manipulated\nvia metal node modification. However, how the metal node affects catalysis\nremains unclear. Herein, using first-principles calculations, we provide\nnew mechanistic insight into dual-metal-site catalysis, where the\nrecently synthesized M<sub>1</sub>-CoOAPc materials (M<sub>1</sub> = Co, Ni, Cu; OAPc = octaaminophthalocyanine) are adopted for demonstration.\nThe modeling results explain experimental measurements of Ni- and\nCu-CoOAPc for facilitating oxygen reduction while highlighting a contradiction\nbetween the theoretical and experimental activity of Co-CoOAPc. Remarkably,\nthis contradiction is attributed to the inherent H<sub>2</sub>O adsorption\non Co nodes, which is usually neglected in dual-metal-site studies.\nWe expand M<sub>1</sub>-CoOAPc with other metal nodes and find that\nFe-CoOAPc (involving *H<sub>2</sub>O on the Fe nodes) exhibits a desirable\ntheoretical half-wave potential of 0.82 V, as revealed from constant-potential\nand microkinetic modeling. This work improves the understanding of\ndual-metal-site catalysis by uncovering the impact of environmental\nspecies covering on the secondary site.