Stable Ti₃C₂ MXene-Based Nanofiltration Membrane Prepared by Bridging for Efficient Dye Wastewater Treatment

Transition metal carbides/nitrides (MXenes) nanosheets have emerged as promising candidates for constructing high-performance nanofiltration (NF) membranes for separation processes. However, MXene membranes exhibit limited feasibility due to the instability of their microstructure, which can lead to failure in the filtration process. This study presents a bridging strategy (polyethyleneimine and polydopamine) to prepare a stable titanium carbide (Ti₃C₂) membrane, resulting in superior nanofiltration efficiency. Polyethyleneimine intercalation can inhibit the tendency to swell, while polydopamine enhances the force between the substrate and nanosheets. The optimized membrane possesses a permeate flux of 112.3 L m^-2 h^-1 bar^-1 (1.6 times higher than pristine Ti₃C₂ membrane) and good selectivity (methyl blue rejection rate: ~99.5%; Na₂SO₄ rejection rate: <5.0%). In addition, the prepared membrane has good long-time durability and is more suitable for low pressure nanofiltration. Notably, the bridging strategy is also applicable to various two-dimensional lamellar membranes. This strategy provides a universal method for enhancing the stability of two-dimensional membranes, thereby promoting their practical applications in robust separation processes.