Sonobe Kazutaka, Tominaka Satoshi, Machida Akihiko
Center for Basic Research on Materials, National Institute for Materials Science, Tsukuba, Ibaraki, 305-0044, Japan.
Synchrotron Radiation Research Center, National Institutes for Quantum Science and Technology (QST), SPring-8, Sayo, Hyogo, 679-5148, Japan.
Chemphyschem. 2024 Dec 2;25(23):e202400583. doi: 10.1002/cphc.202400583. Epub 2024 Oct 27.
Nanoscale water plays a pivotal role in determining the properties and functionalities of materials, and the precise control of its quantity and atomic-scale ordered structure is a focal point in nanotechnology and chemistry. Several studies have theoretically discussed the nano-ordered ice within one- or two-dimensional space and without confinement through hydrogen bonds. In particular, the water cluster has been predicted to play a significant role in biomolecules or functional nanomaterials; however, there has been little experimental evidence for their presence in hydrophobic cavities. In this study, the cubane water octamer - the most stable isomer among small water clusters - was detected within the hydrophobic cavities of UiO-66 metal-organic frameworks, revealing the presence of the smallest ice in their hydrophobic cavity, in the absence of hydrogen bonding. This observation contrasts earlier examples of water clusters confined within nanocavities through hydrogen bonds and provides experimental evidence for water-cluster capturing within hydrophobic cavities. Consequently, our renewed understanding of hydrophilicity and hydrophobicity warrants a design re-evaluation of materials for chemical applications, including fuel cells, water harvesting, catalysts, and batteries.
纳米级水在决定材料的性质和功能方面起着关键作用，精确控制其数量和原子尺度的有序结构是纳米技术和化学领域的一个焦点。几项研究已经从理论上讨论了在一维或二维空间中且无限制条件下通过氢键形成的纳米级有序冰。特别是，水簇被预测在生物分子或功能性纳米材料中起重要作用；然而，几乎没有实验证据表明它们存在于疏水腔中。在本研究中，在UiO - 66金属有机框架的疏水腔内检测到了立方烷水八聚体——小水簇中最稳定的异构体，揭示了在没有氢键的情况下其疏水腔内存在最小的冰。这一观察结果与早期通过氢键限制在纳米腔内的水簇实例形成对比，并为疏水腔内捕获水簇提供了实验证据。因此，我们对亲水性和疏水性的重新认识需要对包括燃料电池、集水、催化剂和电池在内的化学应用材料的设计进行重新评估。
