We also investigated if Grand Canonical Monte Carlo (GCMC) simulations had a higher predictive ability of the experimental data than our models by attempting to partially recreate 109 of the experimental ethylene isotherms and 94 of the experimental ethane isotherms (Supporting Information Figure ). We found that the simulations had a significantly worse performance compared to the ML models, with the ethane and ethylene simulations having MAEs of 1.27 and 1.23 mmol/g, respectively, compared to the experimental results. There appears to be some bias in the simulations towards over-estimating uptake, but we note that the simulations both over-and under-estimate adsorption in different systems, suggesting that there is a limit to the improvement that can be made by simply adjusting the forcefield parameters. Although experimental variation among MOF adsorption measurements is a well-known issue and likely contributes to this error, these results highlight the role that ML trained on experimental data can play in increasing the fidelity of in silico investigations to experimental observations. We are also interested in the influence that different features have on the final ANNpredicted uptake and selectivity. We broadly divided the features into metal-centered revised autocorrelations (RACs), linker-centered RACs, full SBU RACs, geometric features and process features (temperature and pressure, see Sec. 2.2). In the ethane model, metal-centered RACs account for 41% of overall importance, followed by linker-centered RACs (26%), geometric descriptors (22%), full SBU RACs (6%), and process descriptors (4%) (Figure ). Examining the individual most important features, 𝑇 ' #$$ $() has the highest importance, suggesting that the bonding environment local to the linker is important for ethane adsorption. Five of the ten most important features are metal-centered difference RACs, suggesting an important influence from the electrostatic environment created by the metal center. Three of the remaining top ten are geometric features, with measurement pressure comprising the final entry.