Accurate Treatment of Electrostatics During Molecular Simulations In Nanoporous Crystals without Assigning Point Charges to Framework Atoms: Application In Material Selection for Flue Gas Separation

Tuesday, October 18, 2011: 12:30 PM
Conrad D (Hilton Minneapolis)
Taku Watanabe and David Sholl, School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA

Molecular simulations are now routinely performed to study gas adsorption and diffusion in metal-organic frameworks (MOFs).  Traditionally, the electrostatic potential energy surface (EPES) in the pore of a MOF is reproduced by assigning the electrostatic charges to the framework atoms.  Despite some recent advance in the charge assignment methods, point charge models are inherently an imperfect representation of the material’s true EPES.  We have shown how the EPES determined directly from DFT calculations without assigning point charges can be used to accurately describe molecular adsorption in MOFs. Examples will be given including adsorption isotherms and molecular diffusivities of CO2 and N2 in selected MOFs including ZIF-8 and ZIF-90.  We will also discuss recent advances in using information from ab initio Molecular Dynamics to find useful information regarding the internal flexibility of MOFs without requiring development of classical force fields. We will show how models based on these methods are being combined with experimental efforts by our collaborators to develop robust, scalable MOF-based membranes for carbon capture.

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