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Synthesis of ε-Keggin-Type Cobaltomolybdate-Based 3D Framework Material and Characterization Using Atomic-Scale HAADF-STEM and XANES

2017; American Chemical Society; Volume: 56; Issue: 4 Linguagem: Inglês

10.1021/acs.inorgchem.6b02748

1520-510X

Takumi Igarashi, Zhenxin Zhang, Terufumi Haioka, Nao Iseki, Norihito Hiyoshi, Norihito Sakaguchi, Chisato Kato, Sadafumi Nishihara, Katsuya Inoue, Akira Yamamoto, Hisao Yoshida, Nao Tsunoji, Wataru Ueda, Tsuneji Sano, Masahiro Sadakane,

Advanced Nanomaterials in Catalysis

We describe the preparation of ε-Keggin-type cobaltomolybdate-based 3D frameworks with sodium cations, NaH9[ε-CoIIMoV8MoVI4O40CoII2], and their characterization by high-resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption fine structure (XAFS) spectroscopy. Atomic-scale HAADF-STEM images of ε-Keggin compounds were obtained for the first time, and positions of Mo and Co were confirmed. Furthermore, clear evidence of the presence of a CoO4 tetrahedron was obtained by X-ray absorption near-edge structure (XANES) analysis. Their characterization clearly revealed that ε-Keggin-type cobaltomolybdate units, [ε-CoMo12O40]n-, constructed by a central CoIIO4 tetrahedron and 12 surrounding MoO6 octahedra, are linked with CoII to form 3D frameworks.