期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 144, 期 42, 页码 19305-19316出版社
AMER CHEMICAL SOC
DOI: 10.1021/jacs.2c06269
关键词
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资金
- Stanford Woods Institute for the Environment [SPO 164153]
- Stanford Natural Gas Initiative [SPO 127222 WZABN]
- National Institutes of Health [R01DK031450]
- Anne T. and Robert M. Bass Stanford Graduate Fellowship
- Research Foundation-Flanders [G0A0321N, 1276021N]
- US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences [DE-AC02-76SF00515]
- DOE Office of Biological and Environmental Research
- National Institutes of Health, National Institute of General Medical Sciences [P41GM103393]
- Stanford University
- Stanford Research Computing Center
In this study, a mononuclear [CuOH](+) active site in the autoreduced zeolite was unambiguously defined, and its reactivity was compared to the previously defined [Cu2O](2+) active site. The increased reactivity of the binuclear site was attributed to electron delocalization over the two Cu cations via the bridging ligand.
The direct conversion of methane to methanol would have a wide reaching environmental and industrial impact. Copper-containing zeolites can perform this reaction at low temperatures and pressures at a previously defined O-2-activated Cu2O](2+) site. However, after autoreduction of the copper-containing zeolite mordenite and removal of the [Cu2O](2+) active site, the zeolite is still methane reactive. In this study, we use diffuse reflectance UV-vis spectroscopy, magnetic circular dichroism, resonance Raman spectroscopy, electron paramagnetic resonance, and X-ray absorption spectroscopy to unambiguously define a mononuclear [CuOH](+) as the CH, reactive active site of the autoreduced zeolite. The rigorous identification of a mononuclear active site allows a reactivity comparison to the previously defined [Cu2O](2+) active site. We perform kinetic experiments to compare the reactivity of the [CuOH](+) and [Cu2O](2+) sites and find that the binuclear site is significantly more reactive. From the analysis of density functional theory calculations, we elucidate that this increased reactivity is a direct result of stabilization of the [Cu2OH](2+) H-atom abstraction product by electron delocalization over the two Cu cations via the bridging ligand. This significant increase in reactivity from electron delocalization over a binudear active site provides new insights for the design of highly reactive oxidative catalysts.
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