Structure-activity correlation of Ti2CT2 MXenes for C–H activation

Abstract

As a bourgeoning class of 2D materials, MXenes have recently attracted significant attention within heterogeneous catalysis for promoting reactions such as hydrogen evolution and C-H activation. However, the catalytic activity of MXenes is highly dependent on the structural configuration including termination groups and their distribution. Therefore, understanding the relation between structure and activity is desired for the rational design of MXenes as high-efficient catalysts. Here, we present that the correlation between the structure and activity of Ti₂CT₂ (T is a combination of O, OH and/or F) MXenes for C-H activation can be linked by a quantitative descriptor: the hydrogen affinity (E_H). A linear correlation is observed between the mean hydrogen affinity and the overall ratio of O terminations (x_O) in Ti2CT2 MXenes, in which hydrogen affinity increases as the x_O decreases, regardless to the species of termination groups. In addition, the hydrogen affinity is more sensitive to the presence of OH termination than F terminations. Moreover, the linear correlation between the hydrogen affinity and the activity of Ti₂CT₂ MXenes for C-H activation of both -CH₃ and -CH₂- groups can be extended to be valid for all three possible termination groups. Such a correlation provides fast prediction of the activity of general Ti₂CT₂ MXenes, avoiding tedious activation energy calculations. We anticipate that the findings have the potential to accelerate the development of MXenes for heterogeneous catalysis applications.