(21d) Impact of Surface Heterogeneity on the Accuracy of IAST Predictions

To progress toward more energy-efficient adsorption-based processes, it is imperative to have precise multi-component data reflecting real-world conditions. The Ideal Adsorbed Solution Theory (IAST) is widely used due to its simplicity, and its limitations and inaccuracies in less ideal adsorption systems have been noted. In this study, we explore amine-functionalized versions of the UiO-66 structure to modulate the internal surface's homogeneity for the adsorption of carbon dioxide and ethylene. While it might be intuitive to assume that a higher number of functional groups leads to increased heterogeneity, potentially leading to less accurate IAST predictions, our findings challenge this notion. We discovered a mixed-linker system with augmented heterogeneity in terms of added adsorption sites, where IAST predictions align remarkably well with experimental loadings. Our research emphasizes the significance of incorporating uncertainty analysis into IAST predictions to assess their accuracy. Through energetic investigations and Grand Canonical Monte Carlo simulations, we revealed nearly homogeneous carbon dioxide adsorption but heterogeneous ethylene adsorption within the mixed-linker material. This heterogeneity resulted in localized, nearly pure phases of the individual components.