Materials Research Center for Element Strategy, Tokyo Institute of Technology , 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.
ACCEL, Japan Science and Technology Agency , 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan.
J Am Chem Soc. 2017 Nov 29;139(47):17089-17097. doi: 10.1021/jacs.7b08252. Epub 2017 Nov 15.
The development of transition metal intermetallic compounds, in which active sites are incorporated in lattice frameworks, has great potential for modulating the local structure and the electronic properties of active sites, and enhancing the catalytic activity and stability. Here we report that a new copper-based intermetallic electride catalyst, LaCuSi, in which Cu sites activated by anionic electrons with low work function are atomically dispersed in the lattice framework and affords selective hydrogenation of nitroarenes with above 40-times higher turnover frequencies (TOFs up to 5084 h) than well-studied metal-loaded catalysts. Kinetic analysis utilizing isotope effect reveals that the cleavage of the H-H bond is the rate-determining step. Surprisingly, the high carrier density and low work function (LWF) properties of LaCuSi enable the activation of hydrogen molecules with extreme low activation energy (E = 14.8 kJ·mol). Furthermore, preferential adsorption of nitroarenes via a nitro group is achieved by high oxygen affinity of LaCuSi surface, resulting in high chemoselectivity. The present efficient catalyst can further trigger the hydrogenation of other oxygen-containing functional groups such as aldehydes and ketones with high activities. These findings demonstrate that the transition metals incorporated in the specific lattice site function as catalytically active centers and surpass the conventional metal-loaded catalysts in activity and stability.
过渡金属金属间化合物的发展，其中活性位点被纳入晶格框架，具有很大的潜力来调节活性位点的局部结构和电子特性，并提高催化活性和稳定性。在这里，我们报告了一种新的基于铜的金属间化合物电质催化剂 LaCuSi，其中通过具有低功函数的阴离子电子激活的 Cu 位点在晶格框架中原子分散，并提供了对硝基芳烃的选择性加氢，其周转率频率（TOF 高达 5084 h）比经过充分研究的负载金属催化剂高 40 倍以上。利用同位素效应进行的动力学分析表明，H-H 键的断裂是速率决定步骤。令人惊讶的是，LaCuSi 的高载流子密度和低功函数（LWF）特性使得可以用极低的活化能（E = 14.8 kJ·mol）来激活氢分子。此外，LaCuSi 表面的高氧亲和力实现了对硝基芳烃的优先吸附，通过硝基基团实现了高化学选择性。目前的高效催化剂可以进一步引发具有高活性的其他含氧官能团如醛和酮的加氢反应。这些发现表明，嵌入特定晶格位点的过渡金属作为催化活性中心，在活性和稳定性方面超过了传统的负载金属催化剂。
