Determining Physicochemical Properties of Metal-Organic Framework (MOF)–Electrolyte Interfaces

Metal-organic frameworks (MOF) are a diverse, highly tunable and porous materials class that are of interest across fields as diverse as energy conversion and storage, gas adsorption, and drug delivery. For electrochemical-based energy conversion and storage and catalytic applications, there is need to understand the nature of the MOF interface with electrolyte solutions. Here, we develop and implement a series of equilibrium and non-equilibrium molecular dynamics (MD) simulations to elucidate the interfacial interactions that take place at the MOF-solution interface. As a paradigmatic MOF, we examine the interface of the zeolitic imidazolate framework 8 (ZIF-8) MOF with acetonitrile-based electrolyte solutions. The electrolyte salts include LiPF₆, and TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy)-PF₆, and mixtures thereof; the latter two models use TEMPO to represent an electroactive molecule undergoing charge/discharge. To expedite the model throughput, we also report on the development of QSolFlow (QSF), a Python platform to automate MD simulations by creating a high throughput, highly parallelized, MD workflow. QSF allows for rapid generation of MD-derived data that can be used to facilitate the generation of chemical descriptors for machine learning models.