Sustainable MXene membranes for ion sieving and antibacterial water purification

The increasing global water crisis has prompted the development of next-generation separation technologies, with two-dimensional materials such as transition metal carbides/nitrides (MXenes) offering promising options for high-performance membranes. Recent advances have improved MXene membrane fabrication and performance, yet challenges remain in developing more sustainable exfoliation routes and multifunctional designs that combine efficient separation with biofouling resistance. In this work, Ti<inf>3</inf>C<inf>2</inf>T<inf>x</inf> MXene nanosheets were synthesized from MAX phase precursors via hydrofluoric acid etching, followed by liquid-phase exfoliation in Cyrene – a bioderived solvent that significantly reduces oxidation and enhances the colloidal stability of the nanosheets. Within this framework, our approach represents a step towards a more sustainable MXene membrane fabrication process, enabled by a green exfoliation solvent. The resulting dispersions yielded few-layered nanosheets suitable for membrane fabrication, assembled by vacuum filtration on polyvinylidene fluoride porous supports. The membranes attained a compact and defect-free stacked lamellar morphology that formed diffusion pathways, critical for ion transport. Ion transport studies revealed that sieving capabilities are governed by a combination of size exclusion and electrostatic interactions modulated by the membrane's inner structure and charge. Antibacterial tests with Escherichia coli and Staphylococcus aureus demonstrated significant biofouling resistance, with surface roughness notably influencing biofouling resistance. This study provides key insights into the production and performance of Cyrene-processed MXene membranes, advancing their application in water purification technologies.