DFT-Derived Force Fields for Modeling Hydrocarbon Adsorption in MIL-47(V)

Generic force fields such as UFF and DREIDING are widely used for predicting molecular adsorption and diffusion in metal–organic frameworks (MOFs), but the accuracy of these force fields is unclear. We describe a general framework for developing transferable force fields for modeling the adsorption of alkanes in a nonflexible MIL-47­(V) MOF using periodic density functional theory (DFT) calculations. By calculating the interaction energies for a large number of energetically favorable adsorbate configurations using DFT, we obtain a force field that gives good predictions of adsorption isotherms, heats of adsorption, and diffusion properties for a wide range of alkanes and alkenes in MIL-47­(V). The force field is shown to be transferable to related materials such as MIL-53­(Cr) and is used to calculate the free-energy differences for the experimentally observed phases of MIL-53­(Fe)