Abstract
We propose theoretically that the reactivity of O2-bound Cu-ZSM-5 toward methane is enhanced by the presence of one water molecule near a dinuclear copper site inside a 10-membered ring of the zeolite cavity. The current study employed density functional theory (DFT) calculations with the B3LYP functional to elucidate reaction intermediates during dioxygen activation by Cu-ZSM-5 in the presence of one water molecule attached to a dicopper site. The initial event is the formation of a hydroperoxo species bridged by the dicopper site via an H atom transfer from an attached water to the bound dioxygen. After the formation of the intermediate, the hydroperoxo O-O bond is completely cleaved to form radical oxygen containing intermediates, such as a Cu-O-Cu species bound by two OH groups (HO-Cu-O-Cu-OH), as well as a copper oxyl group containing intermediate (HO-Cu-OH-CuO). The radical oxygen containing intermediates can cleave a methane C-H bond in a homolytic fashion. Examining the barrier for the C-H bond activation obtained from DFT calculations, we found that the two types of intermediates have the power to more effectively cleave methane C-H bonds than the Cu-O-Cu intermediate that has been proposed to be formed in the absence of a water molecule. The current DFT findings propose that O2-bound Cu-ZSM-5 in the presence of one water molecule is a potential candidate for catalysts desired for methane to methanol conversion under mild conditions. Recently, techniques for controlling the number of water molecules near the active site of a ZSM-5 zeolite have been developed, and therefore the DFT findings should stimulate experimental efforts for constructing catalysts for direct methane hydroxylation. (Chemical Equation Presented).
| Original language | English |
|---|---|
| Pages (from-to) | 2487-2495 |
| Number of pages | 9 |
| Journal | ACS Catalysis |
| Volume | 6 |
| Issue number | 4 |
| DOIs | |
| Publication status | Published - Apr 1 2016 |
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Keywords
- C-H bond activation
- DFT calculations
- direct methane oxidation
- nanometer sized cavity
- zeolite
ASJC Scopus subject areas
- Catalysis
Cite this
Roles of Water Molecules in Modulating the Reactivity of Dioxygen-Bound Cu-ZSM-5 toward Methane : A Theoretical Prediction. / Yumura, Takashi; Hirose, Yuuki; Wakasugi, Takashi; Kuroda, Yasushige; Kobayashi, Hisayoshi.
In: ACS Catalysis, Vol. 6, No. 4, 01.04.2016, p. 2487-2495.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Roles of Water Molecules in Modulating the Reactivity of Dioxygen-Bound Cu-ZSM-5 toward Methane
T2 - A Theoretical Prediction
AU - Yumura, Takashi
AU - Hirose, Yuuki
AU - Wakasugi, Takashi
AU - Kuroda, Yasushige
AU - Kobayashi, Hisayoshi
PY - 2016/4/1
Y1 - 2016/4/1
N2 - We propose theoretically that the reactivity of O2-bound Cu-ZSM-5 toward methane is enhanced by the presence of one water molecule near a dinuclear copper site inside a 10-membered ring of the zeolite cavity. The current study employed density functional theory (DFT) calculations with the B3LYP functional to elucidate reaction intermediates during dioxygen activation by Cu-ZSM-5 in the presence of one water molecule attached to a dicopper site. The initial event is the formation of a hydroperoxo species bridged by the dicopper site via an H atom transfer from an attached water to the bound dioxygen. After the formation of the intermediate, the hydroperoxo O-O bond is completely cleaved to form radical oxygen containing intermediates, such as a Cu-O-Cu species bound by two OH groups (HO-Cu-O-Cu-OH), as well as a copper oxyl group containing intermediate (HO-Cu-OH-CuO). The radical oxygen containing intermediates can cleave a methane C-H bond in a homolytic fashion. Examining the barrier for the C-H bond activation obtained from DFT calculations, we found that the two types of intermediates have the power to more effectively cleave methane C-H bonds than the Cu-O-Cu intermediate that has been proposed to be formed in the absence of a water molecule. The current DFT findings propose that O2-bound Cu-ZSM-5 in the presence of one water molecule is a potential candidate for catalysts desired for methane to methanol conversion under mild conditions. Recently, techniques for controlling the number of water molecules near the active site of a ZSM-5 zeolite have been developed, and therefore the DFT findings should stimulate experimental efforts for constructing catalysts for direct methane hydroxylation. (Chemical Equation Presented).
AB - We propose theoretically that the reactivity of O2-bound Cu-ZSM-5 toward methane is enhanced by the presence of one water molecule near a dinuclear copper site inside a 10-membered ring of the zeolite cavity. The current study employed density functional theory (DFT) calculations with the B3LYP functional to elucidate reaction intermediates during dioxygen activation by Cu-ZSM-5 in the presence of one water molecule attached to a dicopper site. The initial event is the formation of a hydroperoxo species bridged by the dicopper site via an H atom transfer from an attached water to the bound dioxygen. After the formation of the intermediate, the hydroperoxo O-O bond is completely cleaved to form radical oxygen containing intermediates, such as a Cu-O-Cu species bound by two OH groups (HO-Cu-O-Cu-OH), as well as a copper oxyl group containing intermediate (HO-Cu-OH-CuO). The radical oxygen containing intermediates can cleave a methane C-H bond in a homolytic fashion. Examining the barrier for the C-H bond activation obtained from DFT calculations, we found that the two types of intermediates have the power to more effectively cleave methane C-H bonds than the Cu-O-Cu intermediate that has been proposed to be formed in the absence of a water molecule. The current DFT findings propose that O2-bound Cu-ZSM-5 in the presence of one water molecule is a potential candidate for catalysts desired for methane to methanol conversion under mild conditions. Recently, techniques for controlling the number of water molecules near the active site of a ZSM-5 zeolite have been developed, and therefore the DFT findings should stimulate experimental efforts for constructing catalysts for direct methane hydroxylation. (Chemical Equation Presented).
KW - C-H bond activation
KW - DFT calculations
KW - direct methane oxidation
KW - nanometer sized cavity
KW - zeolite
UR - http://www.scopus.com/inward/record.url?scp=84963739937&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84963739937&partnerID=8YFLogxK
U2 - 10.1021/acscatal.5b02477
DO - 10.1021/acscatal.5b02477
M3 - Article
AN - SCOPUS:84963739937
VL - 6
SP - 2487
EP - 2495
JO - ACS Catalysis
JF - ACS Catalysis
SN - 2155-5435
IS - 4
ER -