Electron-deficient carborane covalent organic framework as an efficient SPME coating for enhanced determination of polycyclic aromatic hydrocarbons.

In this study, carborane covalent organic framework (CB-TAPM) with electron-deficient structure was synthesized and applied as coating material for solid-phase microextraction (SPME) fibers. The extraction efficiency of CB-TAPM COF-coated fibers for polycyclic aromatic hydrocarbons (PAHs) was systematically evaluated and demonstrated superiority over other investigated COF-coated fibers and commercial fibers. The superior enrichment capacity and selectivity of the fabricated fibers for PAHs were attributable to unique electron-deficient boron-rich mesoporous framework and high surface area, which can provide multiple interactions (e.g. hydrophobic effects, π-π stacking, B-Hδ-···Hδ+-C and size-matching effects) with the target analytes. Under the optimized conditions, the developed SPME/GC-MS/MS method demonstrated excellent linearity for target PAHs, with determination coefficients (R²) ranging from 0.9917 to 0.9999 across the calibration curves. The method achieved detection limits (LODs, S/N = 3) of 11-15 pg g-1 for PAHs in milk and 0.24-0.36 pg mL-1 in water samples, demonstrating exceptional sensitivity for complex matrices. Additionally, the fabricated fibers exhibited high repeatability (RSD < 8.6%, n = 5), and reproducibility (inter-batch RSD < 7.8%, n = 5) and reusability (>150 extraction-desorption cycles). This study demonstrates a sustainable and novel methodology for PAH extraction and analysis, while simultaneously broadening the scope of COF-based coatings for SPME applications.