Modulated construction of imine-based covalent organic frameworks for efficient adsorption of polycyclic aromatic hydrocarbons from honey samples

Herein, we introduce a modulation strategy for the synthesis of imine based covalent organic frameworks (COFs) via the condensation of benzene-1,3,5-tricarbaldehyde with 1,3,5-tris (4-aminophenyl) benzene, whereby aniline was adopted as the monofunctional competitor. The introduction of aniline resulted in an enhanced crystallinity, surface area and pore volume, which is beneficial for the enrichment capability of the resulting COFs for the analytes. The optimized COF with the best extraction ability was selected as the solid phase microextraction (SPME) fiber coating for the extraction of polycyclic aromatic hydrocarbons (PAHs) from honey samples. The adsorbed PAHs were then analyzed by gas chromatography with mass spectrometric detection. The merits for the method include: (a) low limits of detection (0.06–0.17 ng/g, S/N = 3), (b) high enrichment factors (290-1566-fold), good reproducibility (relative standard deviations less than 8.4%) and excellent method recoveries for the PAHs (83.0%–116.0%). The enrichment performance of the COFs towards the PAHs could be attributed to the hydrophobic interaction, the high surface area and pore volume of the COF materials.