Sub-nm-confined synthesis of nanoaggregates in 2D MXene membranes for on-demand separation of dyes and salts from water

Advanced 2D MXene membranes endowed with size-adjustable transport pathways are greatly desired for tailored separation scenarios. How to construct such membranes in a facile way remains challenging. Herein, we develop an innovative strategy to prepare the MXene-based membranes with stable and highly tunable transport pathways for multiple separation scenarios through sub-nm-confined synthesis. By simply soaking the pristine MXene membranes in the mixed solution of tannic acid (TA) and 3-aminopropyltriethoxysilane (APTES), the chemical reaction of TA and APTES occurred in the sub-nm-scaled interlayer channels of the MXene membranes, inducing the generation of TA-APTES nanoaggregates. The interlayer spacings of the membranes can be continuously regulated in the range of 13.9–17.1 Å, while the water permeances are designated as between 10.5 and 317 L/(m 2  h bar). Moreover, the membranes are capable of effectively rejecting 89.9 % of NaCl or 98.2 % of MgSO 4 or 100 % of dyes on demand. The developed strategy of sub-nm-confined synthesis makes the constructed membranes much more stable than previously reported ones and suitable to the high-efficient separation of dye/salt mixtures. The intercalated membranes outperform most of other nanofiltration membranes in separating either NaCl or MgSO 4 or dye/salt mixtures. This work paves a new and facile way to construct advanced 2D membranes with desired transport pathways for multiple separation scenarios.