英国曼彻斯特大学Sihai Yang团队报道了还原二氧化氮的金属有机框架中原子级分散的铜位。相关研究成果于2021年7月19日发表于国际一流学术期刊《美国化学会杂志》。

金属有机框架（MOF）材料由于其结构的多样性、固有的孔隙率和可设计的功能性，为制备单原子催化剂提供了良好的平台。然而，由于表征方法的局限性和缺乏直接的结构信息，对原子分散的金属位点的明确鉴定以及它们在催化中的作用的阐明具有挑战性。

该文中，研究人员报告了UiO-66中原子分散的铜中心在室温催化还原NO2中的结构和作用的全面研究。利用高角度环形暗场扫描透射电镜、电子顺磁共振波谱和非弹性中子散射证实了UiO-66上铜位的原子色散，并用中子粉末衍射和固态核磁共振波谱确定了铜位的位置。Cu/UiO-66催化剂在25℃不使用还原剂的情况下对NO2的还原表现出优异的催化性能。在非热等离子体活化下，NO2转化率为97%，形成N2的选择性为88%，使用寿命>50小时，且表现出前所未有的转换频率6.1h^–1。原位和操作红外光谱、固态核磁共振和电子顺磁共振谱揭示了铜位在NO2分子吸附和活化中的关键作用，其中{Cu（I）··NO}和{Cu··NO2}加合物的形成促进了NO2向N2的转化。

该研究将通过详细阐明单原子催化剂在催化中的作用，为进一步设计和研究新型高效的NO2减排催化剂提供启示。

附：英文原文

Title: Atomically Dispersed Copper Sites in a Metal–Organic Framework for Reduction of Nitrogen Dioxide

Author: Yujie Ma, Xue Han, Shaojun Xu, Zi Wang, Weiyao Li, Ivan da Silva, Sarayute Chansai, Daniel Lee, Yichao Zou, Marek Nikiel, Pascal Manuel, Alena M. Sheveleva, Floriana Tuna, Eric J. L. McInnes, Yongqiang Cheng, Svemir Rudi, Anibal J. Ramirez-Cuesta, Sarah J. Haigh, Christopher Hardacre, Martin Schrder, Sihai Yang

Issue&Volume: July 19, 2021

Abstract: Metal–organic framework (MOF) materials provide an excellent platform to fabricate single-atom catalysts due to their structural diversity, intrinsic porosity, and designable functionality. However, the unambiguous identification of atomically dispersed metal sites and the elucidation of their role in catalysis are challenging due to limited methods of characterization and lack of direct structural information. Here, we report a comprehensive investigation of the structure and the role of atomically dispersed copper sites in UiO-66 for the catalytic reduction of NO2 at ambient temperature. The atomic dispersion of copper sites on UiO-66 is confirmed by high-angle annular dark-field scanning transmission electron microscopy, electron paramagnetic resonance spectroscopy, and inelastic neutron scattering, and their location is identified by neutron powder diffraction and solid-state nuclear magnetic resonance spectroscopy. The Cu/UiO-66 catalyst exhibits superior catalytic performance for the reduction of NO2 at 25 °C without the use of reductants. A selectivity of 88% for the formation of N2 at a 97% conversion of NO2 with a lifetime of >50 h and an unprecedented turnover frequency of 6.1 h–1 is achieved under nonthermal plasma activation. In situ and operando infrared, solid-state NMR, and EPR spectroscopy reveal the critical role of copper sites in the adsorption and activation of NO2 molecules, with the formation of {Cu(I)···NO} and {Cu···NO2} adducts promoting the conversion of NO2 to N2. This study will inspire the further design and study of new efficient single-atom catalysts for NO2 abatement via detailed unravelling of their role in catalysis.

DOI: 10.1021/jacs.1c03036

Source: https://pubs.acs.org/doi/10.1021/jacs.1c03036