The effect of atomic point charges on adsorption isotherms of CO2 and water in metal organic frameworks

Kristina Sladekova, Christopher Campbell, Calum Grant, Ashleigh J. Fletcher, José R. B. Gomes, Miguel Jorge

Research output: Contribution to journalArticle

Abstract

The interactions between metal-organic frameworks (MOFs) and adsorbates have been increasingly predicted and studied by computer simulations, particularly by Grand-Canonical Monte Carlo (GCMC), as this method enables comparing the results with experimental data and also provides a degree of molecular level detail that is difficult to obtain in experiments. The assignment of atomic point charges to each atom of the framework is essential for modelling Coulombic interactions between atoms in the MOF and between the MOF and the adsorbate. Such interactions are important in adsorption of polar gases like water or carbon dioxide, both of which are central in carbon capture processes. The aim of this work is to systematically investigate the effect of varying atomic point charges on adsorption isotherm predictions, identify the underlying trends, and based on this knowledge to improve existing models in order to increase the accuracy of gas adsorption prediction in MOFs. Adsorption isotherms for C02 and water in several MOFs were generated with GCMC, using the same computational parameters for each material except point charge sets that were obtained through a wide range of computational approaches. We carried out this work for 6 widely studied MOFs; IRMOF-I, MIL-47, UiO-66, CuBTC, Co-MOF-74 and SIFSIX-2-Cu-1. We included both MOFs with and without open metal sites (OMS), specifically to investigate whether this property affects the predicted adsorption behaviour. Our results show that point charges obtained from quantum mechanical calculations on fully periodic structures are generally more consistent and reliable than those obtained from either cluster-based QM calculations or semi-empirical approaches. Furthermore, adsorption in MOFs that contain OMS is much more sensitive to the point charge values, with particularly large variability being observed for water adsorption 111 such MOFs. This suggests that particular care must be taken when simulating adsorption of polar molecules in MOFs with open metal sites to ensure that accurate results are obtained.
Original languageEnglish
Number of pages23
JournalAdsorption
Early online date7 Dec 2019
DOIs
Publication statusE-pub ahead of print - 7 Dec 2019

Fingerprint

Adsorption isotherms
isotherms
Metals
adsorption
Water
metals
water
Adsorption
Adsorbates
polar gases
Atoms
Gas adsorption
Carbon capture
Periodic structures
interactions
predictions
dioxides
Carbon Dioxide
atoms
carbon dioxide

Keywords

  • metal-organic frameworks
  • adsorbates
  • computer simulations
  • atomic point charges
  • Coulombic interactions

Cite this

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title = "The effect of atomic point charges on adsorption isotherms of CO2 and water in metal organic frameworks",
abstract = "The interactions between metal-organic frameworks (MOFs) and adsorbates have been increasingly predicted and studied by computer simulations, particularly by Grand-Canonical Monte Carlo (GCMC), as this method enables comparing the results with experimental data and also provides a degree of molecular level detail that is difficult to obtain in experiments. The assignment of atomic point charges to each atom of the framework is essential for modelling Coulombic interactions between atoms in the MOF and between the MOF and the adsorbate. Such interactions are important in adsorption of polar gases like water or carbon dioxide, both of which are central in carbon capture processes. The aim of this work is to systematically investigate the effect of varying atomic point charges on adsorption isotherm predictions, identify the underlying trends, and based on this knowledge to improve existing models in order to increase the accuracy of gas adsorption prediction in MOFs. Adsorption isotherms for C02 and water in several MOFs were generated with GCMC, using the same computational parameters for each material except point charge sets that were obtained through a wide range of computational approaches. We carried out this work for 6 widely studied MOFs; IRMOF-I, MIL-47, UiO-66, CuBTC, Co-MOF-74 and SIFSIX-2-Cu-1. We included both MOFs with and without open metal sites (OMS), specifically to investigate whether this property affects the predicted adsorption behaviour. Our results show that point charges obtained from quantum mechanical calculations on fully periodic structures are generally more consistent and reliable than those obtained from either cluster-based QM calculations or semi-empirical approaches. Furthermore, adsorption in MOFs that contain OMS is much more sensitive to the point charge values, with particularly large variability being observed for water adsorption 111 such MOFs. This suggests that particular care must be taken when simulating adsorption of polar molecules in MOFs with open metal sites to ensure that accurate results are obtained.",
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The effect of atomic point charges on adsorption isotherms of CO2 and water in metal organic frameworks. / Sladekova, Kristina; Campbell, Christopher; Grant, Calum; Fletcher, Ashleigh J.; Gomes, José R. B.; Jorge, Miguel.

In: Adsorption, 07.12.2019.

Research output: Contribution to journalArticle

TY - JOUR

T1 - The effect of atomic point charges on adsorption isotherms of CO2 and water in metal organic frameworks

AU - Sladekova, Kristina

AU - Campbell, Christopher

AU - Grant, Calum

AU - Fletcher, Ashleigh J.

AU - Gomes, José R. B.

AU - Jorge, Miguel

PY - 2019/12/7

Y1 - 2019/12/7

N2 - The interactions between metal-organic frameworks (MOFs) and adsorbates have been increasingly predicted and studied by computer simulations, particularly by Grand-Canonical Monte Carlo (GCMC), as this method enables comparing the results with experimental data and also provides a degree of molecular level detail that is difficult to obtain in experiments. The assignment of atomic point charges to each atom of the framework is essential for modelling Coulombic interactions between atoms in the MOF and between the MOF and the adsorbate. Such interactions are important in adsorption of polar gases like water or carbon dioxide, both of which are central in carbon capture processes. The aim of this work is to systematically investigate the effect of varying atomic point charges on adsorption isotherm predictions, identify the underlying trends, and based on this knowledge to improve existing models in order to increase the accuracy of gas adsorption prediction in MOFs. Adsorption isotherms for C02 and water in several MOFs were generated with GCMC, using the same computational parameters for each material except point charge sets that were obtained through a wide range of computational approaches. We carried out this work for 6 widely studied MOFs; IRMOF-I, MIL-47, UiO-66, CuBTC, Co-MOF-74 and SIFSIX-2-Cu-1. We included both MOFs with and without open metal sites (OMS), specifically to investigate whether this property affects the predicted adsorption behaviour. Our results show that point charges obtained from quantum mechanical calculations on fully periodic structures are generally more consistent and reliable than those obtained from either cluster-based QM calculations or semi-empirical approaches. Furthermore, adsorption in MOFs that contain OMS is much more sensitive to the point charge values, with particularly large variability being observed for water adsorption 111 such MOFs. This suggests that particular care must be taken when simulating adsorption of polar molecules in MOFs with open metal sites to ensure that accurate results are obtained.

AB - The interactions between metal-organic frameworks (MOFs) and adsorbates have been increasingly predicted and studied by computer simulations, particularly by Grand-Canonical Monte Carlo (GCMC), as this method enables comparing the results with experimental data and also provides a degree of molecular level detail that is difficult to obtain in experiments. The assignment of atomic point charges to each atom of the framework is essential for modelling Coulombic interactions between atoms in the MOF and between the MOF and the adsorbate. Such interactions are important in adsorption of polar gases like water or carbon dioxide, both of which are central in carbon capture processes. The aim of this work is to systematically investigate the effect of varying atomic point charges on adsorption isotherm predictions, identify the underlying trends, and based on this knowledge to improve existing models in order to increase the accuracy of gas adsorption prediction in MOFs. Adsorption isotherms for C02 and water in several MOFs were generated with GCMC, using the same computational parameters for each material except point charge sets that were obtained through a wide range of computational approaches. We carried out this work for 6 widely studied MOFs; IRMOF-I, MIL-47, UiO-66, CuBTC, Co-MOF-74 and SIFSIX-2-Cu-1. We included both MOFs with and without open metal sites (OMS), specifically to investigate whether this property affects the predicted adsorption behaviour. Our results show that point charges obtained from quantum mechanical calculations on fully periodic structures are generally more consistent and reliable than those obtained from either cluster-based QM calculations or semi-empirical approaches. Furthermore, adsorption in MOFs that contain OMS is much more sensitive to the point charge values, with particularly large variability being observed for water adsorption 111 such MOFs. This suggests that particular care must be taken when simulating adsorption of polar molecules in MOFs with open metal sites to ensure that accurate results are obtained.

KW - metal-organic frameworks

KW - adsorbates

KW - computer simulations

KW - atomic point charges

KW - Coulombic interactions

U2 - 10.1007/s10450-019-00187-2

DO - 10.1007/s10450-019-00187-2

M3 - Article

JO - Adsorption

JF - Adsorption

SN - 0929-5607

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