Covalently bridged MXene/COF hybrid membrane toward efficient dye separation

Two-dimensional (2D) MXene-based membranes combine unique atomic thickness, well-arranged interlayer channel, and have received growing attention in molecular/ion separation and transport. The low permeability and instability of MXene-based membranes in water purification enable it difficult to be utilized in practical processing. Here, we present a high water-permeability and long-lived MXene membrane by assembling 2D heterostructured MXene/COF flakes on macroporous polymeric support. The intercalation of COFs into the interlayer of Ti3C2Tx nanosheets not only increases the adjacent interlayer space, but also provides abundant molecular sieving pores, thereby enhancing the permeability of MXene membrane. While being applied in removal of organic dyes, the MXene/COF hybrid membrane exhibits a superior water permeance (up to ∼ 300 L m-2h−1 bar−1), and several satisfactorily rejections for different dyes (98.2 % for congo red, 98.7 % for chrome black T, 96.4 % for methyl blue, and 97.2 % for methyl orange) are simultaneously achieved. Additionally, the covalent anchoring of COFs on MXene surface can greatly improve the stability. The reduction of hydrophilicity of MXene surface mitigates water molecular absorption on the fluid channel wall and endow the membrane with well swell tolerance in aqueous environment. Such high performance MXene/COF hybrid membrane is mainly caused by the physical sieving mechanism supported by the repulsive interaction, as well as adsorption capability originating from porous COFs. This work provides an alternative approach for the fabrication of high performance MXene-based membranes used for highly effective dye wastewater treatment, and extends the application of 2D membranes in desalination, pollutant treatments, and resource recovery.