Simultaneously tuning interlayer spacing and termination of MXenes by Lewis-basic halides

The surface and interface chemistry are of significance on controlling the properties of two-dimensional transition metal carbides and nitrides (MXenes). Numerous efforts have been devoted to the regulation of Ti₃C₂T_x MXene, however, tuning interlayer spacing and surface halogen termination of other MXenes (besides Ti₃C₂T_x) is rarely reported while demanded. Here we propose a Lewis-basic halides treatment, which is capable of simultaneously engineering the interlayer spacing and surface termination of various MXenes. Benefited from the abundant desolvated halogen anions and cations in molten state Lewis-basic halides, the -F termination was substituted by nucleophilic reaction and the interlayer spacing was enlarged. Ti₃C₂T_x MXene treated by this method showed a high specific capacity of 229 mAh g^-1 for Li⁺ storage, which is almost 2 times higher than pristine one. Considering the universality, our method provides an approach to regulating the properties of MXenes, which may expand their potential applications in energy storage, optoelectronics and beyond.