With their strong confining porosity and versatile surface chemistry, zeolitic imidazolate frameworks—including the prototypical ZIF-8—display exceptional properties for various applications. In particular, the forced intrusion of water at high pressure (∼25 MPa) into ZIF-8 nanopores is of interest for energy storage. Such a system reveals also ideal to study experimentally water dynamics and thermodynamics in an ultrahydrophobic confinement. Here, we report on neutron scattering experiments to probe the molecular dynamics of water within ZIF-8 nanopores under high pressure up to 38 MPa. In addition to an overall confinement-induced slowing down, we provide evidence for strong dynamical heterogeneities with different underlying molecular dynamics. Using complementary molecular simulations, these heterogeneities are found to correspond to different microscopic mechanisms inherent to vicinal molecules located in strongly adsorbing sites (ligands) and other molecules nanoconfined in the cavity center. These findings unveil a complex microscopic dynamics, which results from the combination of surface residence times and exchanges between the cavity surface and center.

中文翻译：

---

超疏水纳米约束中侵入水的异质微观动力学：中子散射和分子建模

凭借其强大的限制孔隙率和通用的表面化学，沸石咪唑酯骨架（包括原型 ZIF-8）在各种应用中显示出卓越的性能。特别是，在高压（~25 MPa）下强制水侵入 ZIF-8 纳米孔对能量存储很有意义。这样的系统也揭示了实验研究超疏水限制中的水动力学和热力学的理想选择。在这里，我们报告了中子散射实验，以在高达 38 MPa 的高压下探测 ZIF-8 纳米孔内水的分子动力学。除了整体限制引起的减速之外，我们还提供了具有不同潜在分子动力学的强动力学异质性的证据。使用互补分子模拟，发现这些异质性对应于位于强吸附位点（配体）的邻近分子和纳米限制在腔中心的其他分子所固有的不同微观机制。这些发现揭示了一个复杂的微观动力学，它是由表面停留时间和腔表面与中心之间的交换结合产生的。