Role of covalent and non-covalent Mg-MOF–PANI/SPANI interactions in enhancing PES ultrafiltration membrane morphology and antifouling performance

In this study, novel ultrafiltration (UF) membranes were developed by incorporating magnesium-based metal–organic frameworks (Mg-MOFs) coated with polyaniline (PANI) and sulfonated polyaniline (SPANI) within a polyethersulfone (PES) matrix. The objective was to address the persistent trade-off between permeability and fouling resistance in conventional UF membranes. The hybrid fillers significantly improved membrane morphology, hydrophilicity, and separation performance. ATR–FTIR and FESEM analyses confirmed the successful integration and uniform dispersion of the hybrid fillers, thereby enhancing the pore structure and interfacial compatibility. DFT analysis confirmed that sulfonation improves interfacial compatibility and electronic interactions, enhancing the performance of Mg-MOF@SPANI-modified PES membranes. The addition of Mg-MOF@SPANI at 5 wt% yielded the best performance, resulting in a well-developed asymmetric structure with increased porosity (up to 51 %) and a reduced water contact angle (down to 54°), indicating excellent surface wettability. Consequently, the pure water flux increased by over 60 % compared to neat PES, reaching a maximum of 270 L/m²·h. The modified membranes also exhibited outstanding antifouling properties, with a flux recovery ratio (FRR) exceeding 86 % and a significantly lower irreversible fouling resistance. Furthermore, the membranes maintained high humic acid rejection (>95 %) while minimizing foulant adsorption. These improvements are attributed to the synergistic effects of the MOF's high porosity and the hydrophilic functional groups of the conducting polymer shell, which together promote the formation of a stable hydration layer and enhance pore connectivity. This work demonstrates that incorporating Mg-MOF@SPANI hybrid fillers is a promising strategy for fabricating next-generation UF membranes with superior permeability, fouling resistance, and operational stability for efficient water treatment.