Low-coordinate Cu1–N2 sites in single-atom catalyst for highly efficient propylene epoxidation with molecular oxygen

Due to its sustainability, direct epoxidation of propylene into propylene oxide (PO) with molecular oxygen alone is believed to be an ideal route. Despite constant research efforts, numerous catalysts struggle with the trade-off between activity and selectivity, which typically results in poor PO yield. In this contribution, we presented an atomically distributed Cu catalyst that had precisely controlled Cu–N coordination numbers of 1:2, termed as Cu 1 –N 2 SAC. In contrast to traditional Cu-based oxide catalysts, this catalyst features exclusive Cu–N coordination, replacing all Cu–O interactions. The synthesized Cu 1 –N 2 SAC catalyst acquired an unprecedented PO formation rate of 5.9 mmolPO gcat –1 h –1 at 275 °C, outperforming any other catalysts reported so far. Sophisticated characterizations and density functional theory calculations revealed that the enhanced catalytic performance was attributed to exclusively forming the electrophilic oxygen species without nucleophilic oxygen species. As a result, these electrophilic oxygen species preferentially target the C=C bond instead of α C–H bond in propylene. These insights pave the way for a new avenue in the optimization of metal oxide catalysts through the precise manipulation of metal-nitrogen (M–N) coordination environments.