多金属氧酸盐
化学
烧结
催化作用
星团(航天器)
金属有机骨架
活动站点
配体(生物化学)
贵金属
金属
纳米技术
化学工程
物理化学
有机化学
程序设计语言
工程类
计算机科学
受体
生物化学
吸附
材料科学
作者
Zhihengyu Chen,S. M. Gulam Rabbani,Qin Liu,Wentuan Bi,Jiaxin Duan,Zhiyong Lu,Neil M. Schweitzer,Rachel B. Getman,Joseph T. Hupp,Karena W. Chapman
摘要
Single-site catalysts (SSCs) achieve a high catalytic performance through atomically dispersed active sites. A challenge facing the development of SSCs is aggregation of active catalytic species. Reducing the loading of these sites to very low levels is a common strategy to mitigate aggregation and sintering; however, this limits the tools that can be used to characterize the SSCs. Here we report a sintering-resistant SSC with high loading that is achieved by incorporating Anderson–Evans polyoxometalate clusters (POMs, MMo6O24, M = Rh/Pt) within NU-1000, a Zr-based metal–organic framework (MOF). The dual confinement provided by isolating the active site within the POM, then isolating the POMs within the MOF, facilitates the formation of isolated noble metal sites with low coordination numbers via exsolution from the POM during activation. The high loading (up to 3.2 wt %) that can be achieved without sintering allowed the local structure transformation in the POM cluster and the surrounding MOF to be evaluated using in situ X-ray scattering with pair distribution function (PDF) analysis. Notably, the Rh/Pt···Mo distance in the active catalyst is shorter than the M···M bond lengths in the respective bulk metals. Models of the active cluster structure were identified based on the PDF data with complementary computation and X-ray absorption spectroscopy analysis.
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