Force Field Development from Periodic Density Functional Theory Calculations for Gas Separation Applications Using Metal–Organic Frameworks

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• 作者：Rocio Mercado ; Bess Vlaisavljevich ; Li-Chiang Lin ; Kyuho Lee ; Yongjin Lee ; Jarad A. Mason ; Dianne J. Xiao ; Miguel I. Gonzalez ; Matthew T. Kapelewski ; Jeffrey B. Neaton ; Berend Smit
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：June 16, 2016
• 年：2016
• 卷：120
• 期：23
• 页码：12590-12604
• 全文大小：949K
• 年卷期：0
• ISSN：1932-7455

文摘

We present accurate force fields developed from density functional theory (DFT) calculations with periodic boundary conditions for use in molecular simulations involving Mb>2b>(dobdc) (M-MOF-74; dobdc^4– = 2,5-dioxidobenzenedicarboxylate; M = Mg, Mn, Fe, Co, Ni, Zn) and frameworks of similar topology. In these systems, conventional force fields fail to accurately model gas adsorption due to the strongly binding open-metal sites. The DFT-derived force fields predict the adsorption of COb>2b>, Hb>2b>O, and CHb>4b> inside these frameworks much more accurately than other common force fields. We show that these force fields can also be used for Mb>2b>(dobpdc) (dobpdc^4– = 4,4′-dioxidobiphenyl-3,3′-dicarboxylate), an extended version of MOF-74, and thus are a promising alternative to common force fields for studying materials similar to MOF-74 for carbon capture applications. Furthermore, it is anticipated that the approach can be applied to other metal–organic framework topologies to obtain force fields for different systems. We have used this force field to study the effect of contaminants such as Hb>2b>O and Nb>2b> upon these materials’ performance for the separation of COb>2b> from the emissions of natural gas reservoirs and coal-fired power plants. Specifically, mixture adsorption isotherms calculated with these DFT-derived force fields showed a significant reduction in the uptake of many gas components in the presence of even trace amounts of Hb>2b>O vapor. The extent to which the various gases are affected by the concentration of Hb>2b>O in the reservoir is quantitatively different for the different frameworks and is related to their heats of adsorption. Additionally, significant increases in COb>2b> selectivities over CHb>4b> and Nb>2b> are observed as the temperature of the systems is lowered.