Finding MOFs for Highly Selective CO₂/N₂ Adsorption Using Materials Screening Based on Efficient Assignment of Atomic Point Charges

Abstract

Electrostatic interactions are a critical factor in the adsorption of quadrupolar species such as CO(2) and N(2) in metal-organic frameworks (MOFs) and other nanoporous materials. We show how a version of the semiempirical charge equilibration method suitable for periodic materials can be used to efficiently assign charges and allow molecular simulations for a large number of MOFs. This approach is illustrated by simulating CO(2) and N(2) adsorption in ~500 MOFs; this is the largest set of structures for which this information has been reported to date. For materials predicted by our calculations to have promising adsorption selectivities, we performed more detailed calculations in which accurate quantum chemistry methods were used to assign atomic point charges, and molecular simulations were used to assess molecular diffusivities and binary adsorption isotherms. Our results identify two MOFs, experimentally known to be stable upon solvent removal, that are predicted to show no diffusion limitations for adsorbed molecules and extremely high CO(2)/N(2) adsorption selectivities for CO(2) adsorption from dry air and from gas mixtures typical of dry flue gas.

Computational exploration of metal–organic frameworks for CO2/CH4 separation via temperature swing adsorption

“…The intrinsic nature of such types of materials makes them have many potential advantages over traditional adsorbents in systematically and precisely modulating their framework topologies and surface chemistry (Stock and Biswas, 2012;Cohen, 2012;Gagnon et al, 2012). Both experimental and theoretical investigations have shown that MOFs can serve as a uniquely ideal platform for the separation of CO 2 from various gas mixtures (Bastin et al, 2008;Couck et al, 2009;Bae et al, 2008;McDonald et al, 2012;Yang et al, 2013a;Burtch et al, 2013;Yazaydın et al, 2009;Liu and Smit, 2009;Haldoupis et al, 2012;Karra and Walton, 2010). However, most of studies available so far are performed to evaluate their performance via PSA/VSA processes (Yang et al, 2011b;Bae and Snurr, 2011;Wilmer et al, 2012;Mu et al, 2010;Pirngruber et al, 2012;Krishna and Van Baten, 2011b), while research efforts are seldom conducted in the scope of TSA approach.…”

Molecular Simulations for Adsorption-Based CO2 Separation Using Metal Organic Frameworks

“…In 2012, Sholl's group [75] used GCMC simulations to calculate adsorption of CO 2 and N 2 in 500 different MOFs. This was the largest set of structures for which this information has been reported until 2012.…”

CO2Adsorption in Fe2(dobdc): A Classical Force Field Parameterized from Quantum Mechanical Calculations

“…55 The Localization of Properties (LoProp) 56 approach was chosen to compute the point charges. The LoProp approach was also used to extract dipoles, quadrupoles, and polarizabilities.…”