Quasielastic neutron scattering study on proton dynamics assisted by water and ammonia molecules confined in MIL-53.

IF 2.3 2区物理与天体物理 Q3 CHEMISTRY, PHYSICAL Structural Dynamics-Us Pub Date : 2021-10-12 eCollection Date: 2021-09-01 DOI:10.1063/4.0000122

Satoshi Miyatsu, Maiko Kofu, Akihito Shigematsu, Teppei Yamada, Hiroshi Kitagawa, Wiebke Lohstroh, Giovanna Simeoni, Madhusudan Tyagi, Osamu Yamamuro

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Abstract

Dynamics of water and other small molecules confined in nanoporous materials is one of the current topics in condensed matter physics. One popular host material is a benzenedicarboxylate-bridging metal (III) complex abbreviated to MIL-53, whose chemical formula is M(OH)[C₆H₂(CO₂)₂R₂] where M = Cr, Al, Fe and R = H, OH, NH₂, COOH. These materials absorb not only water but also ammonia molecules. We have measured the quasi-elastic neutron scattering of MIL-53(Fe)-(COOH)₂·2H₂O and MIL-53(Fe)-(COOH)₂·3NH₃ which have full guest occupancy and exhibit the highest proton conductivity in the MIL-53 family. In a wide relaxation time region (τ = 10^-12-10^-8 s), two relaxations with Arrhenius temperature dependence were found in each sample. It is of interest that their activation energies are smaller than those of bulk H₂O and NH₃ liquids. The momentum transfer dependence of the relaxation time and the temperature dependence of the relaxation intensity suggest that the proton conduction is due to the Grotthuss mechanism with thermally excited H₂O and NH₃ molecules.

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对限制在 MIL-53 中的水和氨分子辅助质子动力学的准弹性中子散射研究。

纳米多孔材料中封闭的水和其他小分子的动力学是当前凝聚态物理学的研究课题之一。一种流行的宿主材料是苯二甲酸桥接金属 (III) 复合物，简称 MIL-53，其化学式为 M(OH)[C6H2(CO2)2R2]，其中 M = Cr、Al、Fe，R = H、OH、NH2、COOH。这些材料不仅能吸收水，还能吸收氨分子。我们测量了 MIL-53(Fe)-(COOH)2-2H2O 和 MIL-53(Fe)-(COOH)2-3NH3的准弹性中子散射，它们具有完全的客体占有率，在 MIL-53 系列中表现出最高的质子传导性。在较宽的弛豫时间区域（τ = 10-12-10-8 秒）内，在每个样品中都发现了两种与阿伦尼乌斯温度相关的弛豫。值得注意的是，它们的活化能小于块状 H2O 和 NH3 液体的活化能。弛豫时间的动量传递依赖性和弛豫强度的温度依赖性表明，质子传导是由于热激发 H2O 和 NH3 分子的 Grotthuss 机制。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Structural Dynamics-Us CHEMISTRY, PHYSICALPHYSICS, ATOMIC, MOLECU-PHYSICS, ATOMIC, MOLECULAR & CHEMICAL

CiteScore

5.50

自引率

3.60%

发文量

审稿时长

16 weeks

期刊介绍： Structural Dynamics focuses on the recent developments in experimental and theoretical methods and techniques that allow a visualization of the electronic and geometric structural changes in real time of chemical, biological, and condensed-matter systems. The community of scientists and engineers working on structural dynamics in such diverse systems often use similar instrumentation and methods. The journal welcomes articles dealing with fundamental problems of electronic and structural dynamics that are tackled by new methods, such as: Time-resolved X-ray and electron diffraction and scattering, Coherent diffractive imaging, Time-resolved X-ray spectroscopies (absorption, emission, resonant inelastic scattering, etc.), Time-resolved electron energy loss spectroscopy (EELS) and electron microscopy, Time-resolved photoelectron spectroscopies (UPS, XPS, ARPES, etc.), Multidimensional spectroscopies in the infrared, the visible and the ultraviolet, Nonlinear spectroscopies in the VUV, the soft and the hard X-ray domains, Theory and computational methods and algorithms for the analysis and description of structuraldynamics and their associated experimental signals. These new methods are enabled by new instrumentation, such as: X-ray free electron lasers, which provide flux, coherence, and time resolution, New sources of ultrashort electron pulses, New sources of ultrashort vacuum ultraviolet (VUV) to hard X-ray pulses, such as high-harmonic generation (HHG) sources or plasma-based sources, New sources of ultrashort infrared and terahertz (THz) radiation, New detectors for X-rays and electrons, New sample handling and delivery schemes, New computational capabilities.