Analysis of the effects of forcefields on adsorption simulation in MOFs

Rights statement
Awarding institution
  • University of Strathclyde
Date of award
  • 2022
Thesis identifier
  • T16414
Person Identifier (Local)
  • 201789169
Qualification Level
Qualification Name
Department, School or Faculty
  • Metal-organic frameworks (MOFs) are crystalline and porous materials consisting of coordination bonds between transition-metal cations and organic ligands. The immense number of existing MOFs poses great challenges for experimental screening. Computational methods like Grand-Canonical Monte Carlo offer a viable alternative for screening, but they rely strongly on the accuracy of the underlying molecular model, or force field. In particular, the assignment of atomic point charges to each atom of the framework is required for modelling Coulombic interactions between the MOF and the adsorbate(s), which are crucial in adsorption of polar compounds. This thesis reports a systematic analysis of the effect of point charges on adsorption predictions by molecular modelling, with the results showing that the use of charges developed by periodic DFT methods produce the most accurate and consistent results. Furthermore, conventional molecular models for adsorption in MOFs neglect important physics of the process, and thus can lead to inaccurate predictions. This is particularly the case for MOFs that possess open metal sites (OMS) – the complex interaction of these sites with particular adsorbate molecules is not captured by standard force fields. The impact of neglecting these interactions can be huge, particularly considering that MOFs that contain OMS are among the most promising materials for gas storage and separation applications, precisely due to these strong and selective binding sites. In this work, experimental adsorption measurements of ethane and ethylene on CuBTC (a widely studied MOF that contains OMS) were carried out and compared to simulations implementing a bespoke model previously developed by our group to account for OMS interactions. This thesis validated the model and demonstrated its robustness even at low temperatures. In summary, the results of this work offer a more consistent way to assess the suitability of molecular models to provide more accurate adsorption predictions.
Advisor / supervisor
  • Jorge, Miguel
Resource Type