Investigation of Guest-Induced Flexibility in Pyrazine Derivative of ALFFIVE MOF via Molecular Simulation

Abstract

One of the important understandings of porous solids like metal−organic frameworks (MOFs) is their flexibility. Therefore, there are certain computational studies on flexible MOFs in the literature, primarily concentrating on MIL-53, UiO-66, and DUT-49. Here, investigation of another class of MOF, that is, [Ni(1,4-pyrazine) 2 (AlF 5 )] n , was shown to have guestinduced flexible characteristics; nevertheless, the mechanism for the emergence of flexibility is uncertain. We simulated the structural flexibility of [Ni(1,4pyrazine) 2 (AlF 5 )] n , named ALFFIVE-Ni-pyr-TBP, upon adsorption of a guest molecule based on force fields using the molecular dynamics (MD) method and Monte Carlo (MC) simulations. As the first step towards understanding guestinduced flexibility, the MC simulations were performed by relaxing the framework and then further comparing it with the rigid framework. Subsequently, MD simulations were executed on the ALFFIVE-Ni-pyr-TBP framework with and without the guest molecules. In the case of moisture adsorption, the MOF system was identified to undergo a geometric transformation from trigonal bipyramidal to square bipyramidal geometry due to the strong interaction of oxygen of the water with the metal aluminum. However, some tilting in the pyrazine ligand was observed in the presence of all the guest molecules. Therefore, the detailed guest-induced flexibility described in this work could support the ALFFIVE series to be explored for future adsorption applications.

Flexible Microporous Framework for One-Step Acquisition of Ethylene from Ternary C2 Hydrocarbons

“…Therefore, flexible MOFs are a promising avenue for future research and development in the realm of porous materials. − The investigation of flexible MOFs not only enhances our understanding of MOF materials but also offers the opportunity to employ them for gas separation and guest capture/release. − Typically, such intriguing sorption patterns are found either at low temperatures (e.g., 77 K for N 2 , 87 K for Ar, or 195 K for CO 2 ) or at high pressures and room temperature. However, it is exceedingly rare to observe the gate-opening isotherms for C 2 hydrocarbons simultaneously at room temperature and low pressure.…”