A Sweet Synthesis\nof MXenes

Two-dimensional transition metal carbides/nitrides (MXenes)\nhave\nshown great promise in various applications. However, mass production\nof MXenes suffers from the excessive use of toxic fluorine-containing\nreagents. Herein, a new method was validated for synthesizing MXenes\nfrom five MAX ceramics. The method features a minimized (stoichiometric)\ndosage of F-containing reagent (NaBF<sub>4</sub>) and polyols (glycerol,\nerythritol, and xylitol) as the reaction solvent. Due to the sweetness\nof polyols and the low environmental impact, we refer to this method\nas a “sweet” synthesis of MXenes. An in-depth molecular\ndynamics simulation study, combined with experimental kinetic parameters,\nfurther revealed that the diffusion of F<sup>–</sup> in the\nconfined interplanar space is rate-determining for the etching reaction.\nThe expansion of interlayer spacing by polyols effectively reduces\nthe diffusion activation energy of F<sup>–</sup> and accelerates\nthe etching reaction.