Photon Factory Activity Report 2017 #35 (2018)

BL-12C, AR-NW10A/2016G093, 2014G060

XAFS Characterization of Ru-MOx Nanoparticles
Transformed from a Grafted Ru12M Porphyrin Complex on SiO2

Satoshi MURATSUGU*1, Atsuki YAMAGUCHI1, Gen-ichi YOKOTA1, Tomoaki MAENO,1
Mizuki TADA1,2
1
Department of Chemistry, Nagoya University, Furo, Chikusa, Aichi 464-8602, Japan.
2
RCMS & IRCCS, Nagoya University, Furo, Chikusa, Aichi 464-8602, Japan.
1 Introduction
Ru-MOx nanoparticles were prepared by the grafting ofporphyrincomplex[1-M,aRu12M{Ru3O(CH3COO)6(Py)2}4 {M(C40H24N8)}] (M = Cu, Ni,Zn) on a pyridine-functionalized SiO2 surface, thestacking of SiO2 matrix overlayers, and hydrogenation at873 K.[1] The local coordination structures of the prepared
Ru-MOx nanoparticles were investigated by Ru and M Kedge XAFS. The 3d metal atoms at the central position ofthe Ru12M porphyrin complex showed great influence onthe structures and catalytic performance of the Ru
nanoparticles.[1]2 Experiment
Ru and M (M = Cu, Ni, Zn) K-edge XAFS of 1-M,SiO2-supported Ru12M complex (2-M), SiO2-matrix
overlayers–stacked Ru12M complex (3-M), and SiO2supported Ru-MOx nanocluster (4-M, only Ru K-edge)
were measured in a transmission mode at 20 K at theNW10A station with a Si(311) double-crystal
monochromator, and at the BL-12C station with a Si(111)
double-crystal monochromator, respectively. M K-edge
XAFS of 4-M was measured in a fluorescence mode at 20
K at the BL-12C station with a Si(111) double-crystal
monochromator and MSSD. EXAFS spectra wereanalyzed using ATHENA and ARTEMIS programs. k3Weighted EXAFS oscillations were Fourier transformed
into R-space, and curve-fitting analysis was performed inR-space with coordination number (CN), interatomicdistance (R), Debye-Waller factor (σ2), and correction-ofedge energy (∆E0). Phase shifts and backscattering
amplitudes were calculated by the FEFF8 code.
3 Results and Discussion
The local coordination structures of 1-M, 2-M, and 3M were examined by Ru and M (M = Cu, Ni, Zn) K-edge
EXAFS analysis, whose k3-weighted EXAFS Fouriertransforms are shown in Figure 1(A) and 1(B). The local
coordination structures of the supported Ru12M porphyrin
complex on 2-M and 3-M were similar to 1-M, indicatingthat the structure of 1-M did not decompose during theattachment. The Ru K-edge EXAFS of 4-M (Figure 1(A))
exhibited a new peak attributed and curve-fitted to Ru-Ru
bond. The small CN value indicated that the size of Ru
nanocluster was very small (ca. 0.8~1.5 nm from STEM
analyses), and the bond length suggested that the most Ru
species were reduced on 4-M. However, the degree ofreduction was dependent on M: 4-Cu was the mostoxidized compared with 4-Ni and 4-Zn from Ru K-edge

XANES. The M K-edge EXAFS of 4-M exhibited theexistence of Cu–O, Ni–O, and Zn–O coordination (Figure1(B)), suggesting the formation of MOx species,respectively.

Figure. 1: (A) k3-Weighted Ru K-edge EXAFS Fouriertransforms of 1-M, 2-M, 3-M, and 4-M. (B) k3-Weighted(1) Cu, (2) Ni, (3) Zn K-edge EXAFS Fourier transformsof 1-M, 2-M, 3-M, and 4-M.
4-Cu exhibited considerable activity in acetophenonehydrogenation (93% conv. (6 h)) compared with 4-Ni(13%) and 4-Zn (40%). The major product was
cyclohexyl methyl ketone, indicating that the aromaticring was reduced more selectively than C=O. The order ofcatalytic activity would have a positive correlation to thatof the oxidation degree of Ru nanoparticles.
References[1] S. Muratsugu, A. Yamaguchi, G. Yokota, T. Maeno, M.
Tada, Chem. Commun. 2018, 54, 4842–4845.
* smuratsugu@chem.nagoya-u.ac.jp