Efficient monitoring of trace phthalate esters in environmental waters using multi-walled carbon nanotubes@Fe₃O₄@MIL-101(Fe) nanocomposites based on magnetic dispersive solid-phase extraction

Phthalate acid esters (PAEs) are endocrine-disrupting contaminants that require reliable trace-level monitoring in environmental waters. Magnetic dispersive solid-phase extraction (MDSPE) offers a green sample-preparation approach, but its performance is often constrained by the limited adsorption capacity, poor structural integrity, limited reusability, and high material cost of existing sorbents. Developing a stable, magnetically responsive, and high-affinity nanocomposite to overcome these limitations remains a critical challenge.

A novel ternary magnetic MWCNTs@Fe₃O₄@MIL-101(Fe) nanocomposite was successfully synthesized via a facile hydrothermal strategy, where multi-walled carbon nanotubes (MWCNTs) serve as a conductive scaffold intertwining Fe₃O₄ nanoparticles and MIL-101(Fe) crystals. This unique architecture endows the sorbent with high saturation magnetization (58.9 emu/g) for rapid separation, a large specific surface area (1127.28 m²/g), and abundant π-electron-rich sites for enhanced adsorption. Under optimized MDSPE conditions coupled with gas chromatography-flame ionization detection (GC-FID), the method achieved wide linear ranges (0.05-2500 μg/L), ultra-low limits of detection (0.005-0.05 μg/L), and satisfactory absolute recoveries (89.5%-110.6%) in real environmental water samples. The sorbent exhibited good reusability (≥90% after five cycles) and excellent precision (RSDs <9.0%). Greenness assessment using the AGREE metric yielded a score of 0.65, reflecting a moderate-to-high level of environmental sustainability.

This work presents a novel "MWCNT-bridged" strategy that successfully integrates magnetic responsiveness, high porosity, and π-π interaction sites into a single, stable sorbent, resolving the common trade-off between functionality and recoverability in magnetic MOF composites. The rationally designed nanocomposite provides a robust, highly sensitive, and environmentally sustainable platform for monitoring trace PAEs in complex aqueous matrices, advancing the development of functional materials for green analytical chemistry.