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(exf), is considered a chemical descriptor of the MXene synthesizability. Here, we show, by density functional theory (DFT) estimations of E(exf) values for 486 different MAX phases, that E(exf) 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(exf) is found to bias, even to govern, the surface chemical activity, evaluated here on the CO(2) adsorption strength, so that more unstable MXenes, displaying larger E(exf) values, display a stronger attachment of species upon.