Free assembly of 2D/2D MXene coupled porous ZnIn₂S₄ heterojunction onto PAN fibrous membrane for breaking through the permeability limitation of O/W emulsion separation and exceptional self-cleaning ability

MXene nanosheets based membrane materials encounter challenges in the field of oil-water separation, including narrow interlayer spacing, insufficient stability, and limited photocatalytic self-cleaning efficiency. To address the aforementioned issues, the 2D/2D MXene nanosheets based heterojunction was constructed through in situ growth of porous ZnIn 2 S 4 and freely assembled onto a PAN fibrous membrane with via vacuum-assisted self-assembly technology. The resulting MXene/ZnIn 2 S 4 @PAN fibrous composite membrane (FCM) exhibited high flux and exceptional photocatalytic self-cleaning property. On the one hand, the porous petal-like structure and intrinsic hydrophilic nature of MXene/ZnIn 2 S 4 heterojunction offered the remarkable nanochannel modulation capability, enabling the composite membrane to achieve high permeability (5471.13 -6732.57   L   m -2 h -1 ) compared with the conventional MXene based composite membranes with compacted lamellar structure. On the other hand, the heterojunction formed between MXene and ZnIn 2 S 4 significantly improved electron conduction efficiency and effectively regulated the energy band structure, as confirmed by electrochemical impedance spectrum and UV–visible near infrared diffuse reflection test. This imparted the composite membrane with exceptional photocatalytic self-cleaning capability for the degradation of organic dyes, with the degradation efficiency reaching as high as 92.15%. Besides, the rational photocatalytic mechanism was proposed on the basis of free radical quenching and EPR experiments. Such high-flux and enhanced self-cleaning PAN FCM showed the potential in dealing with complicated membrane fouling issues and separating emulsified oily wastewater.