Assembling a Metastable Electron Fence within Gold-Zeolite Interfaces for Boosted Propylene Epoxidation

Selective oxidation of hydrocarbons represents a cornerstone reaction in the chemical industry, yet achieving both high activity and selectivity remains challenging. Gold catalysts, renowned for their resistance to overoxidation, are hindered by poor oxygen activation. Here, we develop an "electron fence" strategy to overcome these limitations and enhance the oxidation performances of a conventional gold/zeolite catalyst, which achieves a record-breaking propylene epoxidation rate of 502.6 g·kg_cat^-1·h^-1. By controlling the reduction dynamics and phase separation of immiscible Au-Rh precursors, we engineer a metastable "Hamburger" heterostructure with Rh atomic layers intercalated at the Au-zeolite interface. These interfacial Rh atoms serve as an electron fence and embank electrons within Au, enabling a valence-state transition from Au^m+ to Au^n-. Such electron confinement simultaneously addresses the hydrogen and oxygen activation challenges inherent in traditional Au catalysts, significantly promoting the pivotal generation of hydroperoxyl radicals for selective oxidation. Further fine-tuning the Au-Rh ratio prevents catalyst restructuring that causes propylene overhydrogenation to propane on the ball-cup structure, or overoxidation to CO₂ on Janus configuration. Hence, leveraging the above electronic and geometric promotions, this electron-fence Au-Rh catalyst achieves a two-order-of-magnitude enhancement in epoxidation rates. Such an electron-fence strategy can be extended to propane hydro-oxidation to acetone with simultaneously enhanced activity and selectivity.