They have the general formula Mn+1XnTx, where M is an early transition metal (Ti, Zr, V, Mo, etc.), X is C and/or N, Tx represents the surface functional groups (=O, −OH, −F, −Cl), and n = 1–4.115,116 Some examples include Ti3C2Tx, V2CTx, and Nb2CTx, with over 30 stoichiometric compositions already synthesized with more than 100 predicted.