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Aerobic oxidation of the C–H bond under ambient conditions using highly dispersed Co over highly porous N-doped carbon
- Nie, Renfeng, Chen, Jingwen, Chen, Minda, Qi, Zhiyuan, Goh, Tian-Wei, Ma, Tao, Zhou, Lin, Pei, Yuchen, Huang, Wenyu
- Green chemistry 2019 v.21 no.6 pp. 1461-1466
- carbon, catalysts, chemical bonding, chemoselectivity, cobalt, ethylbenzene, green chemistry, hydrogen, ketones, oxidation, oxygen, pyrolysis, shrinkage, surface area, temperature, volatilization, zinc
- Highly dispersed Co sites in highly porous N-doped carbon (Co-NC) were synthesized by high-temperature pyrolysis of Zn/Co bimetallic zeolitic imidazolate framework-8 (CoₓZn₁₀₀₋ₓ-ZIF). Wide characterization indicated that the pyrolysis atmosphere and temperature play crucial roles in the metal dispersion and pore structure of the resulting materials. A hydrogen treatment at elevated temperatures is found to favour the Zn volatilization and restrict the pore shrinkage of the ZIF precursor, thus yielding efficient catalysts with highly dispersed Co, a high surface area (1090 m² g⁻¹) and pore volume (0.89 cm³ g⁻¹). When used as a catalyst for aerobic oxidation of ethylbenzene (EB), Co₁Zn₉₉-ZIF-800-H₂ contributes to 98.9% EB conversion and 93.1% ketone selectivity under mild conditions (60 °C, 1 atm O₂), which is 41.3 times more active in comparison to the ZIF-67-derived Co catalyst. Co-NC is stable and could be reused four times without obvious deactivation. This catalyst displays good chemoselectivity to the corresponding ketones when using a broad scope of hydrocarbon compounds.