Membranes with ZIF-8 regulated MXene nanosheet stacks for efficient molecular sieving

Abstract

Thin film nanocomposite (TFN) membranes synthesized by introducing nanofillers into a polyamide layer have attracted increasing attentions. However, due to the aggregation of the nanofillers, the fabricated TFN membranes inevitably suffer from a reduced stability. In this work, a novel nanofiltration (NF) selective layer with in-situ formed ZIF-8 was fabricated by an integrated vacuum filtration and interfacial polymerization (IP) method. The d-spacing of MXene nanosheets could be well tailored by controlling the content of in-situ formed ZIF-8 nanoparticles, thus optimizing the surface morphology and chemical composition of the as-prepared NF membrane. The highly hydrophilic MXene nanosheets and controllable ZIF-8 size enabled the molecular sieving ability of the selective layer. Compared with the pristine thin film composite membrane, the optimal membrane exhibited an excellent pure water permeability up to 40.8 L m−2 h−1 bar−1 while maintaining high rejections (>99.0 %) for Congo red, reactive blue 19, xylene brilliant cyaninG250 and methyl blue, respectively. Furthermore, the membranes preserved low salt rejections for Na2SO4, NaCl, MgSO4 and MgCl2. This novel fabrication strategy provides new insights to augment the interlayer distance of 2D nanosheets and broadens the prospects to employ nanofillers inside a membrane matrix for efficient dye/salt separation.