Exfoliation Energy as a Descriptor of MXenes Synthesizability and Surface Chemical Activity

MXenes are two-dimensional nanomaterials isolated from MAX phases by selective extraction of the A component-a p-block element. The MAX exfoliation energy, E, is considered a chemical descriptor of the MXene synthesizability. Here, we show, by density functional theory (DFT) estimations of E values for 486 different MAX phases, that E decreases (i) when MAX is a nitride, (ii) when going along a metal M component d series, (iii) when going down a p-block A element group, and (iv) when having thicker MXenes. Furthermore, E is found to bias, even to govern, the surface chemical activity, evaluated here on the CO₂ adsorption strength, so that more unstable MXenes, displaying larger E values, display a stronger attachment of species upon.