Comparative Study of BiOX (X = Cl, Br, I)/Polyethersulfone Self‐Cleaning Ultrafiltration Membranes Prepared Based on Reverse Thermally Induced Phase Separation Method

To address the trade‐off effect and membrane fouling in conventional polyethersulfone (PES) ultrafiltration membranes, we developed BiOX/PVP/PES (X = Cl, Br, I) composite membranes via reverse thermally induced phase separation (RTIPS) by incorporating hydrophilic polyvinylpyrrolidone (PVP) with bismuth oxyhalide (BiOX) photocatalysts. The BiOI/PVP/PES membrane exhibited optimal performance, achieving a pure water flux of 3750.89 L/(m 2 ·h) and 96.96% humic acid rejection (HA)—significantly surpassing BiOBr and BiOCl‐modified counterparts. Photocatalytic cycling tests confirmed superior self‐cleaning capability, demonstrating a reversible‐to‐total fouling ratio (Rr/Rt) of 0.9 and exceptional antifouling stability. Structural characterization revealed nanoflower‐like BiOI/PVP architectures with hierarchical 3D porosity, providing abundant active sites and an enhanced surface area, which critically enhanced photocatalytic activity and fouling resistance. This work establishes a rational design strategy for high‐flux, self‐cleaning ultrafiltration membranes with synergistic separation and regeneration properties.