Exploring the effect of framework flexibility on water adsorption in the metal-organic framework NbOFFIVE-1-Ni using molecular modeling

Abstract

Many metal-organic frameworks (MOFs) are known to show complex structural flexibility such as breathing, swelling, and linker rotations, and understanding the impact of these structural changes on their guest adsorption properties is important in developing MOFs for practical applications. In this study, we used a multiscale computational approach to provide a molecular-level understanding of how flexibility affects water adsorption in the MOF, NbOFFIVE-1-Ni. This material has narrow pores and good hydrothermal stability, which make it attractive for CO2 capture. We utilized density functional theory (DFT) calculations and grand canonical Monte Carlo (GCMC) simulations to study the impact of NbOFFIVE-1-Ni structural flexibility on its water adsorption at different humidity conditions. Studying the water adsorption in different configurations of NbOFFIVE-1-Ni demonstrated that DFT optimization in the presence of adsorbed water molecules and rotating the linkers are useful strategies to mimic its structural flexibility. Our results illustrate the significance of taking structural flexibility into account when designing MOFs for water adsorption and other relevant applications.