3D Imaging Analysis of Chemical State during Adsorption Processes om MOFs with CT-XAFS Methods

2022 Fiscal Year Final Research Report

• Project/Area Number: 20H02822
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 36010:Inorganic compounds and inorganic materials chemistry-related
• Research Institution: Kyoto University (2022); Nagoya University (2020-2021)
• Principal Investigator: Sakamoto Hirotsohi 京都大学, 高等研究院, 特定講師 (90768649)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: MOF / PCP / XAFSイメージング / 吸着 / 多孔性材料

Outline of Final Research Achievements

In this study, we constructed an adsorption operando XAFS-CT and time-resolved X-ray absorption imaging measurement system to elucidate the adsorption and diffusion behavior of guest molecules inside a single MOF crystal particle, which had not been clarified before. The former method visualized the three-dimensional spatial distribution of adsorbed guest molecules in the crystal at each relative pressure equilibrium state. The latter method visualized the diffusion of MOF-74 in the direction of one-dimensional pores, and the intraparticle diffusion velocity was successfully calculated. These results visualize dynamic and anisotropic adsorption phenomena within a single crystal particle, which could not be seen by conventional crystal structure analysis by diffraction or adsorption isotherms of bulk samples, and lead to an understanding of the adsorption function in real crystals.

Free Research Field

吸着科学 多孔性材料

Academic Significance and Societal Importance of the Research Achievements

本研究は、これまで結晶格子スケール・時間平均にとどまっていたMOF細孔内での反応過程の理解を、メゾスケール・マクロスケール、さらには結晶1粒子全体にまで拡張し、その時間発展の様子を捉えた。メゾ・マクロスケールで時空間分解的に得られる知見を、従来のミクロレベルでの理解と接続した。これにより、MOFのナノ空間機能を我々の現実世界により近いスケールで可視化・理解することで、従来の結晶格子スケールではみられない新現象の発見とその機構解明、それらを利用した機能開発へとつながる。これらを通して、MOFの研究を、従来の「結晶構造の化学」から「実用粒子スケールの材料科学」への展開を促すこと期待できる。