With ordered and adjustable transportation path, two-dimensional (2D) membrane channel assembled by 2D nanosheets with atomic thickness and transverse size of micron have attracted extensive attention in the field of water separation, especially ions selective separation. However, hydrogen bonding makes 2D membrane channel easily swell in aqueous solution, which leads to the destruction of the sieving channel and the loss of membrane interception performance. In this way, its large-scale application is completely restricted. In this study, MXene nanosheets were used as the building units of 2D membranes. The oxygen bridge was formed between the layers to stabilize the interlayer channel through the self-crosslinking treatment. And then, the channel not only gained the capacity of ion sieving, but also effectively resisted swelling effect, making the ion interception and stability both. Furthermore, the 2D MXene laminar channels have exhibited excellent selective separation performance for high-value metal ions (e.g., lithium ions). Here, polystyrene sodium sulfonate (PSS), a chain polymer with sulfonic acid group, was introduced into the laminar structure to realize the selective permeation of Li+ against Na+, K+, and Mg2+ in confined subnanochannels while maintaining stable channel by means of self-crosslinked treatment. In conclusion, 2D MXene laminar channel shows considerable application prospects in the field of ion screening, desalination, energy conversion, and biomimetic artificial channels.

Adjustable structure and ions selective separation performance study of two-dimensional MXene Ti3C2Tx laminar channel

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