MXene nanosheet stacks with tunable nanochannels for efficient molecular separation

Thin film nanocomposite (TFN) membrane, which consists of nanofiller embedded polyamide layer and a porous substrate, have been deemed as a promising candidate to achieve multifunctionality, property enhancement and controllable separation process. Being different from traditional interfacial polymerization synthesis process, this work attempts to use MXene nanosheets as nanofillers on membranes surface while polyamide constructed by interfacial polymerization is served as intercalate reagent and stabilizer. The positively charged polyethyleneimine (PEI) and negatively charged MXene nanosheets guaranteed a favorable compatibility, which finally endowed the obtained membranes with high rejection toward different dyes. The optimal membrane decorated by 0.1 mg PEI and 0.15 mg MXene possesses a pure water permeability of 20.9 LMH bar−1 and dyes rejection of 99.42%, 99.02% and 98.84% for Congo red, Reactive blue 19 and Methyl blue, respectively. Meantime, the membrane exhibited impressive rejections towards Na2SO4 and NaCl (65.7% and 23.9%). The enhanced performance of the MXene-based membrane is mainly due to the amplified interlayer distance and the appropriate crosslinking degree, which increases the water transport and retain the rejection simultaneously. Overall, this work suggests that the employment of MXene nanosheets for the construction of high-performance nanofiltration membranes can be a successful choice to treat dye wastewater.