Robust 3D raspberry-like CdS@MXene heterojunction microsphere reinforced gradient hydrogel-based poly (arylene ether nitrile) membrane with photothermal-catalytic synergy for complex oily emulsified wastewater purification

Hydrogel-based polymer separation membranes are widely applied in the purification of oily emulsified wastewater. However, the traditional hydrogel layer on the membrane surface encounters major obstacles of poor structural stability and difficulty in addressing complex fouling issues. Herein, the 3D raspberry-like CdS@MXene heterojunction microsphere was prepared via a combined strategy of template-assisted and hydrothermal methods, which was applied as a functional nanofiller to reinforce the polyvinyl alcohol-tannic acid (PVA-TA) hydrogel decorated poly (arylene ether nitrile) (PEN) membrane with photothermal-catalytic functionality. Benefiting from the multi-scale synergistic stabilization strategy of multiple bonding, gradient functionalization, and nano-interpenetration enhancement, the hydrogel layer demonstrated robust structural stability under harsh conditions and physical damage. Furthermore, the 3D hierarchical heterojunction microsphere provided a rapid transport pathway for photogenerated electrons and effectively suppressed electron-hole recombination, conferring on the membrane high degradation efficiency of organic dyes under simulated sunlight conditions within 60 min (degradation rate: up to 96.88%). Simultaneously, the membrane surface temperature reached 85.34 °C via rapid photothermal conversion within 30 s, significantly reducing the viscosity of highly viscous oil pollutants attached to the membrane surface and achieving efficient self-cleaning capability. Moreover, 3D MXene-based heterojunction microsphere overcame the compact physical stacking of 2D nanosheets, enabling the efficient separation of oil-in-water emulsions (flux: 215.15 L m −2  h −1 ; rejection rate: 99.56%). This work provides a new approach for preparing robust and multiple antifouling hydrogel-based polymer separation membrane with photothermal-catalytic synergy for treating complex oily emulsified wastewater.