Direct observation of adsorption vibrations of adsorbates on solid surfaces

2018 Fiscal Year Final Research Report

• Project/Area Number: 16H04564
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Catalyst/Resource chemical process
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: Nomura Junko 東京工業大学, 科学技術創成研究院, 准教授 (60234936)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 赤外分光 / 吸着 / 固体表面 / 触媒機能

Outline of Final Research Achievements

In-situ observation of adsorption vibrations was attained by developing the FT-IR spectrometer as well as measurement methods. The shift of cation vibrations over a series of alkaline metal-exchanged zeolite was interpreted in terms of mass and ionic radius of the metal. For molecular cations, the adsorption mode of pyridine derivatives found the independence of the frequency on the mass but the presence of strong effect on the charge of pyridine ring.
Furthermore, the comparison of the same cation vibration over various zeolites with different topologies clarified the presence of "confinement effect" within the limited space of zeolites, which were different by about 50 cm-1, i. e., 0.6 kJ/mol, depending on zeolite topology. This level of energy difference is less than van der Waals interaction, and is in agreement with the recent report from a theoretical calculation study.

Free Research Field

触媒化学、赤外分光

Academic Significance and Societal Importance of the Research Achievements

これまでは、シンクロトロンや特殊な検出器などが用いられていたため、報告例の少ない分子の吸着に由来する振動（400 cm-1以下）を、装置と測定法を開発することでその場観測ができるようにした。ゼオライトはその空間構造やサイズによって吸着分子の「閉じ込め効果」が存在することが示唆されていたが、これを様々なゼオライトを用いて同一種の吸着振動によって直接観測し比較することで、その効果の違い（約50 cm-1, 0.6 kJ/mol）が分子間力に匹敵するエネルギーであることが示唆された。