The “Pull Effect” of a Hanging Zn<sup>II</sup> on Improving the Four‐Electron Oxygen Reduction Selectivity with Co Porphyrin
Jinxiu Han, Huang Tan, Kai Guo, Haoyuan Lv, Xinyang Peng, Wei Zhang, Haiping Lin, Ulf‐Peter Apfel, Rui Cao
Abstract
Abstract 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 Zn II ion. Inspired by Cu/Zn‐superoxide dismutase, we designed and synthesized 1‐CoZn with a hanging Zn II 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 O 2 reduction. With spectroscopic studies, the hanging Zn II was demonstrated to be able to facilitate the electron transfer from Co II to O 2 , through an electronic “pull effect”, to give Co III ‐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 Zn II to improve O 2 activation and O−O bond cleavage.