Recent advances in MXenes: beyond Ti-only systems

Since the first report on Ti 3 C 2 T x in 2011, the number of reports on 2D transition metal carbides and nitrides, known as MXenes, has increased rapidly. Most of the reports have focused on Ti-based MXenes due to their ease of synthesis and striking properties; however, MXenes beyond Ti-only systems have also been recently reported to exhibit intriguing electronic, magnetic, optical, and mechanical properties. This forward-looking review aims to summarize the research trends, synthesis, properties, and applications of non-Ti MXenes to motivate researchers to unearth the characteristics and unleash the full potential of less explored MXenes. Furthermore, the properties and applications of theoretically predicted non-Ti MXenes are also highlighted to stimulate further research in synthesizing them experimentally. Finally, the challenges to be addressed and future research directions are presented. This review provides a comprehensive overview of the research trends in the synthesized and predicted non-Ti MXenes. The synthetic methods, unique properties, applications, and advantages of non-Ti MXenes compared to Ti-based MXenes are discussed.