Emerging subfamilies of MXenes: Modification of M and X sites

Abstract

Since the discovery of Ti₃C₂ in 2011, the family of MXenes expanded tremendously and is now acclaimed to be the fastest-growing family of 2D materials. Their huge compositional design space allows for the frequent addition of new members with unique properties. By altering the parameters in M_n+1X_nT_x, innumerable compositions can be achieved, enabling the tailoring of properties for specific applications. Modifying the M and X sites of MXenes has led to new subfamilies over the last decade, including double transition metal MXenes, high-entropy MXenes, and oxycarbide MXenes, all of which exhibit the potential to outperform the conventional MXenes in various applications. This review provides a comprehensive overview of the latest MXene subfamilies, emphasizing their structure, properties, and applications while addressing current challenges and future research directions in this burgeoning field.