Surface‐Engineered 2D Bimetallic FeNi‐MOFs Derived from Layered Double Hydroxides for Photocatalytic Membranes with Enhanced Dye Fixation in Wastewater Treatment

FeNi-based layered double hydroxides (LDHs) are used as precursors to derive bimetallic FeNi-metal organic frameworks (D-FeNi MOFs) with terephthalic acid ligands, offering enhanced properties compared to conventionally prepared FeNi-MOFs (C-FeNi MOFs). D-FeNi MOFs exhibited superior structural, surface, and electrochemical features, confirmed by density functional theory (DFT) studies, which also predicted their catalytic mechanism. Band edge potential calculations through Mott-Schottky analysis revealed their favorable redox potential, enhanced charge transfer, and reduced recombination resistance, explaining their superior photocatalytic efficiency. D-FeNi MOFs degraded 91% of rhodamine B (RhB) and 89% of Congo red (CR), outperforming C-FeNi MOFs, which degraded 84% and 77%, respectively. These MOFs are incorporated (3, 5, and 7 wt%) into polysulfone (PSU) membranes to develop photocatalytic membranes. The 7 wt% membranes (FNM7) exhibited high water flux (54.4 L m^-2h^-1) and dye flux (≈51.1 and 41.6 L m^-2h^-1) with rejection rates of ≈88% and 90% for RhB and CR, significantly surpassing bare membranes. FNM7 demonstrated superior anti-fouling and photocatalytic regeneration (12.9% RhB, 9.6% CR degradation under sunlight) across three cycles. DFT studies showed FeNi centers weaken dye molecule bonds, aiding degradation, while carboxyl groups in MOFs formed robust hydrogen bonds with PSU, ensuring no particle leaching. This highlights D-FeNi MOF-membranes as an efficient system for wastewater treatment.