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

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 (EB(*OH)) favors the dissociation of H2O into *OH, whereas the transfer of *OH to propylene will be impeded. The scaling relationship of the EB(*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-Hvac), which can be protonated reversibly. During propylene electrooxidation, the strong EB(*OH) on AgPz favors the dissociation of H2O into *OH. Subsequently, the AgPz transforms into AgPz-Hvac that possesses weak EB(*OH), benefiting to the further combination of *OH and propylene. The dynamically reversible interconversion between AgPz and AgPz-Hvac accompanied by changeable EB(*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 mmolPG gcat–1 h–1, which is more than one order of magnitude higher than the highest value ever reported.