Hierarchically spherical assembly of carbon nanorods derived from metal-organic framework as solid-phase...

Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) are pervasive contaminants in aquatic environments. They are characterized by persistence, toxicity, bioaccumulation, and long-range transport, significantly threatening human health. The development of sensitive methods for nitro-PAH analysis in environmental samples is in great need. This study developed a novel carbonaceous SPME coating derived from metal-organic framework (MOF), namely a spherical assembly consisting of carbon nanorods with hierarchical porosity (HP-MOF-C), for the extraction and determination of nitro-PAHs in waters. The HP-MOF-C coated fiber demonstrated superior nitro-PAH extraction efficiencies, with enrichment factors 2∼70 times higher than commercial fibers. This enhancement was due to the strong hydrophobic, π-π electron coupling/stacking, and π-π electron donor-acceptor interactions between the carbonaceous framework of HP-MOF-C and the nitro-PAHs. Moreover, the unique hierarchical porous structure of HP-MOF-C accelerated the diffusion of nitro-PAHs, further facilitating their enrichment. The fiber also exhibited good thermal stability, remarkable chemical stabilities against common acid, base, and polar/non-polar solvents, and long service life (> 150 SPME cycles). The nitro-PAH determination method based on HP-MOF-C coating yielded wide linear ranges, low detection limits (0.4∼5.0 ng L^-1), satisfactory repeatability and reproducibility, and good recoveries in real water samples. The proposed method was considered to be green according to the Analytical GREEnness assessment. The present study not only offers an efficient SPME coating for the enrichment of nitro-PAHs, but also provides insights into the design of porous coating materials.