Recent advances in MXenes: synthesis, properties, applications, and DFT-based investigations

Abstract: MXenes have emerged as a rapidly growing family of two-dimensional (2D) transition-metal carbides, nitrides, and carbonitrides that exhibit a unique combination of excellent electrical conductivity, large specific surface area, outstanding mechanical properties, and tunable surface chemistry. Since their first discovery in 2011 through the selective etching of MAX phases, MXenes have attracted significant attention from both experimental and theoretical research communities. Their distinctive structural characteristics and versatile physicochemical properties have enabled a wide range of applications in energy storage, gas sensing, flexible electronics, environmental remediation, catalysis, biomedicine, and electromagnetic interference shielding. In particular, the presence of abundant surface functional groups and controllable electronic structures provides exceptional opportunities for tailoring their performance for specific technological applications. This review provides a comprehensive overview of MXenes, including their crystal structures, synthesis methods, fundamental properties, and major technological applications. Various synthesis approaches, ranging from conventional chemical etching to emerging electrochemical and molten-salt methods, are discussed. The outstanding electrical, mechanical, chemical, and optical properties of MXenes are highlighted, with particular emphasis on their structure–property relationships. Furthermore, recent advances in MXene-based applications in energy storage systems, gas sensors, environmental technologies, flexible electronics, and electromagnetic shielding are summarized. In addition, the role of density functional theory (DFT) calculations in understanding and predicting the behavior of MXenes is critically reviewed. Theoretical studies on electronic structure engineering, gas adsorption, atomic doping, ion storage, catalysis, and spintronic applications are discussed to demonstrate the importance of first-principles simulations in guiding experimental developments. Overall, MXenes represent a highly promising class of multifunctional materials with enormous potential for next-generation electronic, energy, environmental, and biomedical technologies.