Single-atom site (SA) catalysts on N-doped carbon (CN) materials exhibit prominent performance for their active sites being M-Nx. Due to the commonly random doping behaviors of N species in these CN, it is a tough issue to finely regulate their doping types and clarify their effect on the catalytic property of such catalysts. Herein, we report that the N-doping type in CN can be dominated as pyrrolic-N and pyridinic-N respectively through compounding with different metal oxides. It is found that the proportion of distinct doped N species in CN depends on the acidity and basicity of compounded metal oxide host. Owing to the coordination by pyrrolic-N, the SA Cu catalyst displays an enhanced activity (two-fold) for transfer hydrogenation of quinoline to access the valuable molecule tetrahydroquinoline with a good selectivity (99%) under mild conditions. The higher electron density of SA Cu species induced by the predominate pyrrolic-N coordination benefits the hydrogen transfer process and reduces the energy barrier of the hydrogenation pathway, which accounts for the improved catalytic effeciency. [Figure not available: see fulltext.].
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This work was supported by the National Key R&D Program of China (Nos. 2018YFA0702003 and 2016YFA0202801), the National Natural Science Foundation of China (Nos. 21890383, 21671117, 21871159, and 21901135), the National Postdoctoral Program for Innovative Talents, the Shuimu Tsinghua Scholar, Science and Technology Key Project of Guangdong Province of China (No. 2020B010188002), and Beijing Municipal Science & Technology Commission (No. Z191100007219003). We thank the BL14W1 station in Shanghai Synchrotron Radiation Facility (SSRF) and 1W1B station for XAFS measurement in Beijing Synchrotron Radiation Facility (BSRF).