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Enhancement of CO2binding and mechanical properties upon diamine functionalization of M2(dobpdc) metal-organic frameworks

  • Author(s): Lee, JH
  • Siegelman, RL
  • Maserati, L
  • Rangel, T
  • Helms, BA
  • Long, JR
  • Neaton, JB
  • et al.
Abstract

© 2018 The Royal Society of Chemistry. The family of diamine-appended metal-organic frameworks exemplified by compounds of the type mmen-M2(dobpdc) (mmen = N,N′-dimethylethylenediamine; M = Mg, Mn, Fe, Co, Zn; dobpdc4-= 4,4′-dioxidobiphenyl-3,3′-dicarboxylate) are adsorbents with significant potential for carbon capture, due to their high working capacities and strong selectivity for CO2that stem from a cooperative adsorption mechanism. Herein, we use first-principles density functional theory (DFT) calculations to quantitatively investigate the role of mmen ligands in dictating the framework properties. Our van der Waals-corrected DFT calculations indicate that electrostatic interactions between ammonium carbamate units significantly enhance the CO2binding strength relative to the unfunctionalized frameworks. Additionally, our computed energetics show that mmen-M2(dobpdc) materials can selectively adsorb CO2under humid conditions, in agreement with experimental observations. The calculations further predict an increase of 112% and 124% in the orientationally-averaged Young's modulus E and shear modulus G, respectively, for mmen-Zn2(dobpdc) compared to Zn2(dobpdc), revealing a dramatic enhancement of mechanical properties associated with diamine functionalization. Taken together, our calculations demonstrate how functionalization with mmen ligands can enhance framework gas adsorption and mechanical properties.

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