Dynamically Reversible Interconversion of Molecular Catalysts for Efficient Electrooxidation of Propylene into Propylene Glycol

Jingwen Ke; Mingfang Chi; Jiankang Zhao; Yan Liu; Ruyang Wang; Kaiyuan Fan; Yuxuan Zhou; Zhikai Xi; Xiangdong Kong; Hongliang Li; Jie Zeng; Zhigang Geng

doi:10.1021/jacs.3c00660

Dynamically Reversible Interconversion of Molecular Catalysts for Efficient Electrooxidation of Propylene into Propylene Glycol

J Am Chem Soc. 2023 Apr 26;145(16):9104-9111. doi: 10.1021/jacs.3c00660. Epub 2023 Mar 21.

Authors

Jingwen Ke¹, Mingfang Chi¹, Jiankang Zhao¹, Yan Liu¹, Ruyang Wang¹, Kaiyuan Fan¹, Yuxuan Zhou¹, Zhikai Xi¹, Xiangdong Kong¹, Hongliang Li¹, Jie Zeng^{1

2}, Zhigang Geng¹

Affiliations

¹ Hefei National Research Center for Physical Sciences at the Microscale, Key Laboratory of Strongly-Coupled Quantum Matter Physics of Chinese Academy of Sciences, Key Laboratory of Surface and Interface Chemistry and Energy Catalysis of Anhui Higher Education Institutes, Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, P. R. China.
² School of Chemistry & Chemical Engineering, Anhui University of Technology, Ma'anshan, Anhui 243002, P. R. China.

PMID: 36944146
DOI: 10.1021/jacs.3c00660

Abstract

For the electrooxidation of propylene into 1,2-propylene glycol (PG), the process involves two key steps of the generation of *OH and the transfer of *OH to the C═C bond in propylene. The strong *OH binding energy (E_B(*OH)) favors the dissociation of H₂O into *OH, whereas the transfer of *OH to propylene will be impeded. The scaling relationship of the E_B(*OH) plays a key role in affecting the catalytic performance toward propylene electrooxidation. Herein, we adopt an immobilized Ag pyrazole molecular catalyst (denoted as AgPz) as the electrocatalyst. The pyrrolic N-H in AgPz could undergo deprotonation to form pyrrolic N (denoted as AgPz-H_vac), which can be protonated reversibly. During propylene electrooxidation, the strong E_B(*OH) on AgPz favors the dissociation of H₂O into *OH. Subsequently, the AgPz transforms into AgPz-H_vac that possesses weak E_B(*OH), benefiting to the further combination of *OH and propylene. The dynamically reversible interconversion between AgPz and AgPz-H_vac accompanied by changeable E_B(*OH) breaks the scaling relationship, thus greatly lowering the reaction barrier. At 2.0 V versus Ag/AgCl electrode, AgPz achieves a remarkable yield rate of 288.9 mmol_PG g_cat^-1 h^-1, which is more than one order of magnitude higher than the highest value ever reported.