Carbon nitride supported Fe2 cluster catalysts with superior performance for alkene epoxidation

Shubo Tian,Jian Zhang,Wenxing Chen,Yadong Li,Rong Yu,Jun Luo,Lin Gu,Quanchen Feng,Dingsheng Wang,Qiang Fu,Chen Chen,Weng-Chon Cheong,Qing Peng,Claudia Draxl,Juncai Dong,Zheng Chen

doi:10.1038/s41467-018-04845-x

Abstract

Sub-nano metal clusters often exhibit unique and unexpected properties, which make them particularly attractive as catalysts. Herein, we report a “precursor-preselected” wet-chemistry strategy to synthesize highly dispersed Fe2 clusters that are supported on mesoporous carbon nitride (mpg-C3N4). The obtained Fe2/mpg-C3N4 sample exhibits superior catalytic performance for the epoxidation of trans-stilbene to trans-stilbene oxide, showing outstanding selectivity of 93% at high conversion of 91%. Molecular oxygen is the only oxidant and no aldehyde is used as co-reagent. Under the same condition, by contrast, iron porphyrin, single-atom Fe, and small Fe nanoparticles (ca. 3 nm) are nearly reactively inert. First-principles calculations reveal that the unique reactivity of the Fe2 clusters originates from the formation of active oxygen species. The general applicability of the synthesis approach is further demonstrated by producing other diatomic clusters like Pd2 and Ir2, which lays the foundation for discovering diatomic cluster catalysts.

Highlights

Sub-nano metal clusters often exhibit unique and unexpected properties, which make them attractive as catalysts
First-principles calculations reveal that the unique reactivity of the Fe2 clusters is attributed to the formation of active oxygen species
We investigated the catalytic properties of the as-prepared Fe2/mpgC3N4 sample for epoxidation reactions

Summary

Introduction

Sub-nano metal clusters often exhibit unique and unexpected properties, which make them attractive as catalysts. In current processes for alkene epoxidation in liquids, an extensive use of expensive oxidants or large doses of co-reagents is usually required[22,23,24], which inevitably leads to an increase in the costs. To overcome this drawback, several homogeneous catalysts like iron- and rutheniumsubstituted polyoxometalates have been developed, allowing O2 to be the oxidant without a need for any co-reductant[25,26]. The prepared Fe2/mpgC3N4 sample exhibits excellent catalytic performance toward epoxidation of trans-stilbene, which is absent when using iron porphyrin, single-atom Fe, or small Fe nanoparticles as the catalyst. The synthesis approach reported in this work can be applied to produce other transition-metal dimers and paves the way for a precise design of nanocatalysts at the atomic scale

Methods

Results

Conclusion