Roll‐To‐Roll Fabricating MXene Membranes with Ordered Interlayer Distances For Molecule And Ion Separation

Abstract Application‐oriented assembly of two‐dimensional nanosheets with uniform nanochannels is critical for fabricating sophisticated, high‐performance membranes for water treatment. However, fabricating the desired membranes by a simple, fast, and effective method is a challenge as most of the previous methods are based on batch processes rather than a continuous roll‐to‐roll process. Here, a simple Meyer rod‐coating approach to continuously fabricate large‐size and flat MXene membranes at a scale up to 5 m is introduced. This study demonstrated that a high MXene concentration, above 10 mg mL −1 , is critical in processability due to the desired viscosity, surface tension, and viscoelastic properties. The as‐made MXene membranes show that shearing and solutal‐Marangoni flow can considerably improve the ordering of the stacked MXene nanoflakes. Thus, the rod‐coated MXene membranes demonstrate a smaller surface roughness and interlayer distance compared to the MXene membranes fabricated by the most commonly vacuum‐assisted filtration. The rod‐costed MXene membranes show superior performance in dye and mono/divalent cation separation. The proposed roll‐to‐roll Meyer rod‐coating method can also be used to fabricate MXene‐based composites, such as MXene/carbon nanotubes and MXene/polymer, using the inks containing high concentration MXene and other desired compositions. This roll‐to‐roll method will promote an industry‐level fabrication and application of MXene‐based membranes.