Crosslinked Poly(N‐Hydroxymethyl Acrylamide) Hydrogel@ <scp> Fe ₃ O ₄ </scp> – <scp> MnO

Abstract

This study presents the development of a ternary hydrogel‐based bimetallic nanocomposite (NDM@FM–NC) as an efficient multifunctional material for catalytic applications. Although hydrogels and metal oxide nanoparticles have been extensively explored, integrating them into a single pH‐responsive and catalytically active platform remains challenging. To overcome this limitation, a tunable hydrogel network was synthesized via free‐radical polymerization of N‐hydroxymethyl acrylamide (NHMA), methacrylic acid (MAA), and 2‐(dimethylamino)ethyl acrylate (DMAEA), forming P(NHMA)‐co‐P(DMAEA)‐co‐P(MAA). The incorporation of MAA imparted pH sensitivity, while NHMA enhanced hydrophilicity, structural stability, and crosslinking density. Fe 3 O 4 –MnO 2 bimetallic nanoparticles were synthesized through co‐precipitation followed by hydrothermal treatment and subsequently immobilized within the hydrogel matrix to obtain an efficient heterogeneous catalyst. The synergistic interaction between Fe and Mn species promoted electron transfer and increased the density of active catalytic sites. The structure, morphology, and thermal stability of the nanocomposite were confirmed by FTIR, EDAX, SEM, TEM, TGA, UV–Vis spectroscopy, and powder XRD analyses. Catalytic performance was evaluated using methylene blue as a model dye pollutant. NDM@FM–NC exhibited excellent reduction efficiency (98.18%) with a pseudo‐first‐order rate constant of 0.117 s −1 in the presence of NaBH 4 , while oxidative degradation using H 2 O 2 achieved 98.97% removal with a rate constant of 5.26 × 10 −4  s −1 . These results demonstrate the potential of NDM@FM–NC as a robust and reusable catalyst for wastewater remediation.