Fabrication of photocatalytic antifouling 3D COFs/MXene membrane via oil–oil–water ternary strategy for efficient oil–water separation

With the acceleration of industrialization, oily wastewater poses a serious threat to the ecological environment. Membrane separation technology has emerged as a research hotspot due to its advantages of high efficiency and energy savings; however, membrane fouling significantly restricts its long term stable operation. This study introduces a 3D COFs/MXene composite membrane with photocatalytic self–cleaning capability for highly efficient oil–water separation. A well dispersed 3D COFs colloidal dispersion was prepared via oil–oil–water three phase interfacial polymerization, effectively overcoming the dispersion challenges of COFs materials. Ti 3 C 2 T x MXene nanosheets were synthesized using the LiF/HCl etching method. Using intermolecular hydrogen bonding, the two components were ultrasonically assembled, and a COFs/MXene composite membrane was fabricated via vacuum assisted filtration. The membrane exhibits excellent hydrophilicity (water contact angle as low as 54.3°) and underwater oleophobicity (underwater oil contact angle up to 144.9°). Under visible light irradiation, the MXene component generates reactive oxygen species (·O 2 − and ·OH), enabling photocatalytic degradation of oil contaminants adsorbed on the membrane surface and thereby imparting self–cleaning functionality. Separation performance tests reveal that the composite membrane achieves efficient separation of various oil–in–water emulsions, with a maximum water flux of 1918.9 L m −2 h −1 bar −1 . The flux for n –hexane emulsion increased to 2.1 times that of pure MXene membrane, while maintaining a rejection rate above 98.8%. Moreover, the membrane demonstrates excellent cycling stability and photocatalytic antifouling performance. This research offers a novel strategy for developing self–cleaning separation membranes and holds promising potential for application in oily wastewater treatment.