The “Pull Effect” of a Hanging ZnII on Improving the Four‐Electron Oxygen Reduction Selectivity with Co Porphyrin

Due to the challenge of cleaving O−O bonds at single Co sites, mononuclear Co complexes typically show poor selectivity for the four‐electron (4e−) oxygen reduction reaction (ORR). Herein, we report on selective 4e− ORR catalyzed by a Co porphyrin with a hanged ZnII ion. Inspired by Cu/Zn‐superoxide...

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Published in:Angewandte Chemie International Edition 2024-09, Vol.63 (36), p.e202409793-n/a
Main Authors: Han, Jinxiu, Tan, Huang, Guo, Kai, Lv, Haoyuan, Peng, Xinyang, Zhang, Wei, Lin, Haiping, Apfel, Ulf‐Peter, Cao, Rui
Format: Article
Language:English
Subjects:
Aqueous solutions
bioinspired catalyst
Chemical reduction
Chemical synthesis
Cleavage
Cobalt
Electron transfer
molecular electrocatalysis
O2 binding
oxygen reduction
Oxygen reduction reactions
Porphyrins
pull effect
Selectivity
Superoxide dismutase
Zinc
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Summary:Due to the challenge of cleaving O−O bonds at single Co sites, mononuclear Co complexes typically show poor selectivity for the four‐electron (4e−) oxygen reduction reaction (ORR). Herein, we report on selective 4e− ORR catalyzed by a Co porphyrin with a hanged ZnII ion. Inspired by Cu/Zn‐superoxide dismutase, we designed and synthesized 1‐CoZn with a hanging ZnII at the second sphere of a Co porphyrin. Complex 1‐CoZn is much more effective than its Zn‐lacking analogues to catalyze the 4e− ORR in neutral aqueous solutions, giving an electron number of 3.91 per O2 reduction. With spectroscopic studies, the hanging ZnII was demonstrated to be able to facilitate the electron transfer from CoII to O2, through an electronic “pull effect”, to give CoIII‐superoxo. Theoretical studies further suggested that this “pull effect” plays crucial roles in assisting O−O bond cleavage. This work is significant to present a new strategy of hanging a ZnII to improve O2 activation and O−O bond cleavage. A bioinspired Co porphyrin with a hanging ZnII ion at its second sphere was designed and synthesized. This Zn‐hanged Co porphyrin showed improved selectivity for the four‐electron oxygen reduction reaction in neutral aqueous solutions as compared to its Zn‐lacking analogues. The hanging ZnII ion played crucial roles in promoting O2 binding at the Co porphyrin site and also in facilitating the O−O bond cleavage through an electronic “pull effect”.
ISSN:1433-7851
1521-3773
1521-3773
DOI:10.1002/anie.202409793