The right isotherms for the right reasons? Validation of generic force fields for prediction of methane adsorption in metal-organic frameworks

Abstract

In recent years, the use of computational tools to aid in the evaluation, understanding and design of advanced porous materials for gas storage and separation processes has become evermore widespread. High-performance computing facilities have become more powerful and more accessible and molecular simulation of gas adsorption has become routine, often involving the use of a number of default and commonly used parameters as a result. In this work, we consider the application of molecular simulation in one particular field of adsorption – the prediction of methane adsorption in metal-organic frameworks in the low loading regime – and employ a range of computational techniques to evaluate the appropriateness of many commonly chosen simulation parameters to these systems. In addition to confirming the power of relatively simple generic force fields to quickly and accurately predict methane adsorption isotherms in a range of MOFs, we demonstrate that these force fields are capable of providing detailed molecular-level information which is in very good agreement with quantum chemical predictions. We highlight a number of chemical systems in which molecular-level insight from generic force fields should be approached with a degree of caution and provide some general recommendations for best practice in simulations of CH₄ adsorption in MOFs.

Keywords:

• Methane adsorption
• binding
• DFT
• force field validation
• metal-organic frameworks

Acknowledgements

EB gratefully acknowledges funding from ERC (Consolidator grant 307755 FIN) and EPSRC. The authors acknowledge support from the University of Nottingham’s high-performance computing facilities. This research made use of the Balena High Performance Computing Service at the University of Bath. The authors are grateful to Prof. T. Düren for fruitful discussions on the choice of cut-off radius in LJ interactions.