Two-dimensional carbonitride MXenes: From synthesis to properties and applications

Carbonitride MXenes, such as Ti3CNTx, Ti2C0.5N0.5Tx, and Ti4(C0.2N0.8)3Tx, have attracted much interest in the large family of two-dimensional (2D) nanomaterials. Like their carbide MXene counterparts, the nanolayered structure and functional groups endow carbonitride MXenes with an attractive combination of physical and chemical properties. More interestingly, the replacement of C by N changes the lattice parameters and electron distribution of carbonitride MXenes due to the greater electronegativity of N as compared to C, thus resulting in significantly enhanced functional properties. This paper reviews the development of carbonitride MXenes, the preparation of 2D carbonitride MXenes, and the current understanding of the microstructure, electronic structure, and functional properties of carbonitride MXenes. In addition, applications, especially in energy storage, sensors, catalysts, electromagnetic wave shielding and absorption, fillers, and environmental and biomedical fields, are summarized. Finally, their current limitations and future opportunities are presented. Carbonitride MXenes not only possess a unique nanolayered structure and functional groups but also have varying lattice parameters and electron distribution compared with their carbide counterparts due to the replacement of C by N. These characteristics endow carbonitride MXenes with superior physical and chemical properties, making them increasingly popular in various fields, such as energy, environment, and electromagnetic interference shielding. image