High-performance magnetic COFs for synergistic adsorption–photocatalysis of thiamethoxam and acetamiprid in water

The persistence of neonicotinoid insecticides such as thiamethoxam (THM) and acetamiprid (ACP) in aquatic systems poses significant ecological and health risks, necessitating effective remediation strategies. In this work, we report the synthesis of hydrophilic magnetic covalent organic frameworks (COFs) functionalized with Fe 3 O 4 nanoparticles as integrated adsorbent–photocatalyst systems for simultaneous capture and degradation of THM and ACP. The COFs, engineered with nitrogen-rich, π-conjugated backbones, combine strong π–π stacking, hydrogen bonding, and hydrophobic interactions with high surface area, crystallinity, and magnetic recoverability (confirmed by FT-IR, XRD, BET, and VSM analyses). Fe 3 O 4 @HMN-COF delivered exceptional adsorption performance, achieving maximum capacities of 520 mg/g (THM) and 450 mg/g (ACP), fitting a pseudo-second-order kinetic model and Langmuir monolayer adsorption, with thermodynamic analysis indicating a spontaneous and endothermic process. Under optimized UV conditions (1:1 Fe 3 O 4 :COF ratio, 0.01 g catalyst, pH 11.0, 30 °C), Fe 3 O 4 @HMN-COF achieved 96.2% degradation of THM and 95% of ACP within 5 h, with complete mineralization confirmed by GC–MS and rate constants up to 0.198 h -1 —substantially outperforming conventional adsorbents and photocatalysts. The material retained >85% of its performance over five regeneration cycles and maintained high activity in complex real matrices (honey, fruit extracts), underscoring its structural robustness and selectivity. These results position hydrophilic magnetic COFs as scalable, reusable, and high-efficiency platforms for the sustainable removal of neonicotinoid pesticides from contaminated water. Schematic illustration of the dual-function Fe 3 O 4 @HMN-COF material for synergistic adsorption and photocatalytic degradation of neonicotinoid pesticides (thiamethoxam and acetamiprid) in water. Pesticide molecules are first adsorbed onto the porous COF surface, followed by reactive oxygen species (•OH, •O 2 - )–mediated photocatalytic degradation under UV light, producing CO 2 and H 2 O. The material can be magnetically recovered and reused with high efficiency. • Hydrophilic Fe 3 O 4 @COFs synthesized as dual-function adsorbent–photocatalysts. • Fe 3 O 4 @HMN-COF showed high adsorption (520 mg/g THM; 450 mg/g ACP). • Achieved >95% photocatalytic degradation of THM and ACP under UV in 5 h. • Strong reusability (>85% efficiency after 5 cycles) and matrix robustness. • Synergistic adsorption–photocatalysis offers scalable pesticide remediation.