Self-assembled hierarchical heterogeneous MXene/COF membranes for efficient dye separations

The instability and low permeability of MXene membrane in water treatment are big obstacles for its practical application. In this paper, multilayered porous MXene/COF composite membranes have been prepared by electrostatic self-assembly of MXene and COF-LZU1. The optimal flexible MXene/COF 4:1 composite membrane shows a high water permeance of above 169.3 L m−2 h−1 bar−1 under the separation test of five typical dye aqueous solutions, which are Methyl Green (MG), Ethyl Violet (EVT), Fuchsin Basic (FB), Crystal Violet (CV), Methylene Blue (MB). It also can maintain high dyes rejection and water permeance under various pH systems (i.e. pH = 3, 7 and 11) and two dye concentrations (i.e. 50 mg/L and 250 mg/L). In addition, the UV degradation study shows that MXene/COF 4:1 composite membrane can be recycled by exposing UV light without damage. Such outstanding dye separation performances could be attributed to the hierarchical heterogeneous structure containing micropores and mesopores, as well as strong photothermal conversion ability of the membrane. The novel membrane may broaden the dye separation scope in both academic and industrial fields.