resumo
To ensure that computational screening of porous materials, such as MOFs, for carbon capture yields accurate predictions, it is essential to carefully, and thoroughly, validate and test the underlying molecular models. Yet, such validation studies are extremely scarce in the literature, and the vast majority of comparisons between simulated and experimental adsorption isotherms do not realistically consider the inherent uncertainty in either or both methods. In this paper, we conduct a systematic assessment of simulation force fields by comparing them against 'consensus' experimental isotherms derived from a curated dataset of carbon dioxide adsorption measurements. Our estimate for the average uncertainty in experimental adsorption isotherms is similar to 15 %, while the average uncertainty arising from the choice of framework force field is similar to 10 %; these uncertainties are quite significant and should be considered explicitly when comparing simulations to experiments. Remarkably, we observed that generic force fields taken 'off the shelf' only yielded good predictions of experimental data for one out of five MOFs studied here - IRMOF-1. The observed discrepancies for Cu-BTC and Co-MOF-74 can be explained by the inability of standard force fields to accurately describe the specific interactions of CO2 with open metal sites. In contrast, the differences for UiO-66 can be rationalised by the presence of extensive defects in the MOF structure. However, the disagreement observed for MIL-47 has not been unequivocally explained, raising the need for more extensive experimental and simulation studies of this material. Based on these results, we provide concrete recommendations for future computational modelling studies of adsorption in MOFs.
palavras-chave
COORDINATIVELY UNSATURATED SITES; TOTAL-ENERGY CALCULATIONS; VAPOR-LIQUID-EQUILIBRIA; UNITED-ATOM DESCRIPTION; TRANSFERABLE POTENTIALS; MOLECULAR SIMULATION; PHASE-EQUILIBRIA; GAS-ADSORPTION; CARBON-DIOXIDE; NANOPOROUS MATERIALS
categoria
Chemistry; Science & Technology - Other Topics; Materials Science
autores
McCready, C; Asif, K; Blaney, R; Gomes, JRB; Fletcher, A; Jorge, M
nossos autores
José R. B. Gomes
Investigador PrincipalProjectos
CICECO - Aveiro Institute of Materials (UIDB/50011/2020)
CICECO - Aveiro Institute of Materials (UIDP/50011/2020)
Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)
agradecimentos
The authors are grateful to Prof. Veronique van Speybroeck and her research group for kindly providing input files for defective UiO-66 structures. We are also indebted to the NIST-ISODB team for their incredible effort in compiling and making large amounts of experimental adsorption data publicly available in an easy-to-use format. C.M. acknowledges EPSRC for a PhD studentship (ref EP/R513349/1) . K.A. acknowledges EPSRC and NPL for an iCASE PhD studentship (ref EP/Y528833/1) . J.R.B.G. is thankful to the project CICECO-Aveiro Institute of Materials, refs. UIDB/50011/2020, UIDP/50011/2020 and LA/P/0006/2020, financed by national funds through the FCT/MCTES (PIDDAC) .