Modulated covalent organic frameworks with higher specific surface area for the ultrasensitive detection of polybrominated biphenyls

Controllable construction of covalent organic frameworks (COFs) is fascinating, and full elucidations on the relationships between their microstructures and adsorption performance for persistent organic pollutants (POPs) are imperative and desirable, yet challenging. Herein, the 2,5-dimethoxybenzaldehyde (DB) has been first employed as a modulator to construct COFs with higher specific surface area and enhanced hydrophobicity under the mild conditions, after competing with the building blocks of 2,5-dimethoxyterephaldehyde (DMTP) and 1,3,5-tris(4-aminophenyl)benzene (TAPB). These TAPB-DMTP-DB COFs have been further fabricated as solid phase microextraction (SPME) coatings with uniform morphology and comparative thickness, to investigate their enrichment capacities for POPs systematically. In particular, the DB-modulated COF demonstrated outstanding enrichment factors (4400–11360) for polybrominated biphenyls (PBBs). Moreover, ultrasensitive analytical method has been developed based on the DB-modulated COF-coated fiber and gas chromatography-mass spectrometry (GC–MS), with low limits of detection (0.04–0.28 ng/L), wide linear range (0.25–5000 ng/L), and satisfactory reproducibility, realizing the precise quantifications of ultra-trace PBBs in environmental aqueous samples.