美国阿贡国家实验室Karena W. Chapman团队报道了催化金属有机框架中接近活性中心的分子路径。相关研究成果于2021年11月26日发表在国际顶尖学术期刊《美国化学会杂志》。

分子如何接近、结合和从催化位点释放是多相催化的关键，包括新兴的金属-有机框架（MOF）基催化剂。

研究人员使用原位同步辐射X射线散射来评估NU-1000中具有不同表面功能化的催化Ni-oxo团簇附近试剂和产物分子的主要结合位点，其条件接近催化中使用的条件。反应剂和产物分子在孔隙中的位置可以与乙烯加氢活性联系起来。对于最活跃的催化剂，乙烯试剂分子结合在催化簇附近，但仅在接近实验观察到的催化起始温度时。

乙烷产物分子倾向于不同的结合位置，表明该产物很容易从活性部位释放。记录了框架负热膨胀对客体的不寻常依赖性。研究人员假设试剂和产物结合位点反映了通过MOF到活性位点的途径，并可用于确定影响催化活性的关键因素。

附：英文原文

Title: The Molecular Path Approaching the Active Site in Catalytic Metal–Organic Frameworks

Author: Ana E. Platero-Prats, Andreas Mavrandonakis, Jian Liu, Zhihengyu Chen, Zhijie Chen, Zhanyong Li, Andrey A. Yakovenko, Leighanne C. Gallington, Joseph T. Hupp, Omar K. Farha, Christopher J. Cramer, Karena W. Chapman

Issue&Volume: November 26, 2021

Abstract: How molecules approach, bind at, and release from catalytic sites is key to heterogeneous catalysis, including for emerging metal–organic framework (MOF)-based catalysts. We use in situ synchrotron X-ray scattering analysis to evaluate the dominant binding sites for reagent and product molecules in the vicinity of catalytic Ni-oxo clusters in NU-1000 with different surface functionalization under conditions approaching those used in catalysis. The locations of the reagent and product molecules within the pores can be linked to the activity for ethylene hydrogenation. For the most active catalyst, ethylene reagent molecules bind close to the catalytic clusters, but only at temperatures approaching experimentally observed onset of catalysis. The ethane product molecules favor a different binding location suggesting that the product is readily released from the active site. An unusual guest-dependence of the framework negative thermal expansion is documented. We hypothesize that reagent and product binding sites reflect the pathway through the MOF to the active site and can be used to identify key factors that impact the catalytic activity.

DOI: 10.1021/jacs.1c11213

Source: https://pubs.acs.org/doi/10.1021/jacs.1c11213