Length-controlled hydrophobic CF₃-COF as a highly efficient absorbent coating for dual-mode solid-phase...

Polycyclic aromatic hydrocarbons (PAHs), a group of seriously hazardous environmental contaminants, have attracted extensive attention due to their carcinogenicity, genotoxicity, mutagenicity, and ubiquity. In this work, the excellent hydrophobic trifluoromethyl-enriched covalent organic framework (CF₃-COF) was designed and synthesized as coating of solid-phase microextraction (SPME). The CF₃-COF offered a high adsorption selectivity for PAHs, which could be attributed to the multiple interactions between the CF₃-COF and PAHs, including hydrophobicity interaction, π-π and H bond interactions. Furthermore, headspace (HS) and direct immersion (DI) dual-mode solid-phase microextraction (HS/DI-SPME) were innovatively integrated as a dual-mode extraction by varying the length of SPME coating on stainless-steel, which could simultaneously and efficiently extract 16 PAHs with different volatile. Amazingly, the proposed strategy achieved fast adsorption for PAHs and shortened the adsorption equilibrium time to 15 min. By further integrating with gas chromatography tandem mass spectrometry (GC-MS/MS), PAHs could be detected in the range of 0.008-0.16 ng mL^-1 with a quantitative limit of 0.029-0.47 ng mL^-1, respectively. The recoveries of PAHs in water samples ranged from 80.84 to 117.67 %. This work indicates that the dual-mode CF₃-COF-SPME is a promising candidate for the enrichment of multiple hazardous substances in complicated samples.