As the most abundant and one of the most unique liquids on earth, water exhibits anomalous structural and dynamical properties, and water in confinement displays greater anomalies as the hydrogen-bond network is disrupted. Metal-organic frameworks (MOFs) are another unique class of materials that display high adsorption properties for vapors and liquids. Recently, the MOF Co2Cl2BTDD has been shown to adsorb water at low relative humidity, attracting interest for application in harvesting water from air. In this contribution, we aim to obtain a fundamental understanding of water confined inside the MOF Co2Cl2BTDD. We utilize the many-body potential energy function (MB-pol) to simulate water and calculate theoretical infrared spectra, comparing with experimental infrared spectroscopy measurements. Theoretical analysis elucidates the mechanism of pore filling inside the MOF, with water initially binding to the open metal sites and forming one-dimensional chains bridging the metal sites and the interior of the framework. These chains nucleate pore filling, establishing the hydrogen-bond network and becoming bulk-like. As the pore fills, the spectroscopic features and orientational dynamics transition from “ice-like” to “liquid-like” properties, with water in confinement exhibiting a unique behavior among ice, liquid, and gas.

Understanding the structure and dynamics of water confined inside metal-organic frameworks

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.