(199c) Incorporating Intrinsic Flexibility Effect into MOF Adsorption Properties Simulation at a Low Computational Cost

Computationally predicting the adsorption properties of Metal organic Frameworks (MOF) in a high throughput way has become a useful means of identifying promising materials for chemical separations. In almost all cases, high throughput simulations assume MOF structures as rigid for computational convenience. All MOFs, however, have intrinsic flexibility due to thermal vibration of atoms. Recent studies have suggested that this ubiquitous flexibility may have significant impacts on molecular adsorption in MOFs. Methods have been developed to predict the influence of this type of flexibility on MOF adsorption properties using molecular dynamics (MD) simulations, but these methods are computationally expensive and rely on the existence of reliable force fields.

We will describe a method of estimating the impact of intrinsic flexibility on MOF adsorption, which does not use any force fields for MOF framework. This approach uses experimentally available thermal vibration parameters to provide information about local flexibility. We show how this information can be used to reliably assess whether atomic vibrations make a significant impact on molecular adsorption in MOFs. Data from a variety of single component and binary mixtures adsorbed at dilute and non-dilute conditions forms our test sets. This method creates a useful way to establish the level of detail that is required for molecular modeling of adsorption in experimentally accessible MOFs to give quantitatively reliable results.