Department of Chemistry and Biochemistry, University of California, San Diego, California 92093, United States.
Materials Science and Engineering Program, University of California, San Diego, California 92093, United States.
J Am Chem Soc. 2021 Dec 22;143(50):21189-21194. doi: 10.1021/jacs.1c09097. Epub 2021 Dec 8.
Water capture mechanisms of zeolitic imidazolate framework ZIF-90 are revealed by differentiating the water clustering and the center pore filling step, using vibrational sum-frequency generation spectroscopy (VSFG) at a one-micron spatial resolution and state-of-the-art molecular dynamics (MD) simulations. Through spectral line shape comparison between VSFG and IR spectra, the relative humidity dependence of VSFG intensity, and MD simulations, based on MB-pol, we found water clustering and center pore filling happen nearly simultaneously within each pore, with water filling the other pores sequentially. The integration of nonlinear optics with MD simulations provides critical mechanistic insights into the pore filling mechanism and suggests that the relative strength of the hydrogen bonds governs the water uptake mechanisms. This molecular-level detailed mechanism can inform the rational optimization of metal-organic frameworks for water harvesting.
水捕获沸石咪唑酯骨架 ZIF-90 的机制通过分辨水聚集和中心孔填充步骤来揭示，使用在一微米空间分辨率的振动和和频产生光谱学（VSFG）和最先进的分子动力学（MD）模拟。通过 VSFG 和 IR 光谱之间的光谱线形状比较、VSFG 强度与相对湿度的关系，以及基于 MB-pol 的 MD 模拟，我们发现水聚集和中心孔填充几乎同时发生在每个孔内，水填充其他孔是依次进行的。将非线性光学与 MD 模拟相结合，为孔填充机制提供了关键的机制见解，并表明氢键的相对强度决定了水吸收机制。这种分子水平的详细机制可以为水采集的金属有机骨架的合理优化提供信息。
