Waste coconut shell-derived nitrogen-doped porous carbon synergized with Bi₂MoO₆ for sensitive detection of marbofloxacin in complex matrices

Marbofloxacin (MAR) residues in aquatic environments present a significant threat to both ecological systems and human health. This study presents a novel nanocomposite for the detection of trace MAR, integrating bismuth molybdate (Bi₂MoO₆) with environmentally friendly and cost-effective nitrogen-doped porous biomass carbon (NC), which exhibits high catalytic activity. The NC, derived from waste coconut shells, possesses a high BET specific surface area of 842.72 m² g^-1, offering a hierarchical pore structure for efficient adsorption and electron transport. Bi₂MoO₆ microspheres are uniformly anchored to the NC porous framework, resulting in a collaborative sensing interface characterized by “adsorption–enrichment–catalysis”. In this configuration, NC facilitates rapid electron transport and concentrates target molecules, while Bi₂MoO₆ offers abundant catalytic sites. The resulting Bi₂MoO₆/NC/GCE sensor demonstrates outstanding performance for MAR detection, with a linear range of 0.03–10 µM, a sensitivity of 7.958 µA µM^-1, and a detection limit of 0.0045 µM. Additionally, the sensor exhibits high selectivity, good reproducibility, and stability, successfully detecting trace levels of MAR in tap water and milk, with recoveries ranging from 96.0% to 100.6%. The use of waste coconut shell-derived porous carbon as a renewable precursor, the aqueous-phase synthesis of the Bi₂MoO₆/NC composite, and the avoidance of toxic organic solvents in the electrode preparation and detection process collectively contribute to the green and sustainable nature of the method. This study offers an efficient and environmentally friendly approach for the rapid and reliable detection of trace antibiotics in complex matrices.