@article{Yuan2022, 
author = {Enxian Yuan and Meixia Zhou and Guojun Shi and Panming Jian and Xu Hou},
title = {Ultralow-loading single-atom cobalt on graphitic carbon nitrogen with robust Co-N pairs for aerobic cyclohexane oxidation},
year = {2022},
journal = {Nano Research},
volume = {15},
number = {10},
pages = {8791-8803},
keywords = {single-atom Co, carbon nitride, cyclohexane, catalytic oxidation},
url = {https://www.sciopen.com/article/10.1007/s12274-022-4556-3},
doi = {10.1007/s12274-022-4556-3},
abstract = {Selectively aerobic oxidation of cyclohexane using the homogeneous catalysts is an industrially important process, suffering from the difficult catalyst separation, low conversion and selectivity. Herein, a series of single-atom Co catalysts, possessing the ultralow Co loading of below 1.0 wt.‰, supported on mesoporous graphitic carbon nitrogen (Co/g-C3N4-w) were prepared by a simple adsorption method and applied into the cyclohexane oxidation. Characterization results demonstrate that the confinement effect of the voids in g-C3N4 facilitates the formation of the single-atom Co, which is stabilized by bonding with the pyridinic nitrogen of g-C3N4 and accompanied by the electron transfer from Co to g-C3N4. The catalytic performance presents an increasing trend with the increment of the Co loading, and the superior value with the conversion of 23.8% and selectivity of 95.6% is obtained over Co/g-C3N4-0.9. Kinetic study, density functional theory (DFT) calculations, and characterizations reveal that the decreased activation energy of cyclohexane oxidation over Co/g-C3N4-w can be attributed to the favorable dissociation activation of O2 molecules and decomposition of cyclohexylhydroperoxide (CHHP) intermediate on the coordination unsaturated single-atom Co as well as the enhanced adsorption of cyclohexane on the electron-rich g-C3N4 surface, boosting the cyclohexane oxidation following the surface catalytic mechanism. Distinctively, robust Co-N structures and hydrophobic nature of g-C3N4 contribute to the high stability of Co/g-C3N4-0.9 for cyclohexane oxidation.}
}