ABSTRACT Polyimide (PI) is recognized as a high‐performance biomaterial membrane due to its high mechanical strength, excellent biocompatibility, biological stability, and highly tunable chemical structure. However, the intrinsic hydrophobicity of PI blood fluid contact ultrafiltration (UF) membrane materials poses risks related to separation efficiency and stability, as well as complications arising from biofouling and immune cascades. In this study, benzimidazolium‐based phosphorylated zwitter