Hydrophilic covalent organic frameworks for efficient extraction of p‑phenylenediamine antioxidants and their derived...

p-Phenylenediamines (PPDs) and their transformation products, PPD-derived quinones (PPDQs), are widely present in the environment as tire rubber-derived emerging pollutants. However, their environmental fate and behavior in water environment are still not fully understood due to the lack of effective analytical methods. Herein, three hydrophilic covalent organic frameworks (H-COFs) were synthesized for the extraction of PPDs and PPDQs, via introducing hydroxyl groups into ordered COF frameworks. Of which, TP-DHBD-COF, with more hydrogen bond donor/acceptor sites, exhibits outstanding hydrophilicity (contact angle of 13.9°) as well as rapid adsorption kinetics (10 min) for 6PPD and 6PPDQ, along with excellent adsorption capacities (223 and 244 mg g^-1). Density functional theory calculations unraveled that multiple interactions (including hydrophilic drive, hydrogen bond interactions and π-π interactions) synergistically promoted the adsorption. With TP-DHBD-COF as adsorbent, a dispersive solid-phase extraction-high-performance liquid chromatography-tandem mass spectrometry method was constructed, offering low detection limit (0.2-1.5 pg mL^-1), wide linear range (0.001-50 ng mL^-1), high enrichment factor (16-67), and good recoveries (95.8 %-108.9 %). Eight PPDs and PPDQs in different wharfs along the Yangtze River were quantified for analysis of their environmental behavior. This work not only advances the design of functionalized COF adsorbents, but also pioneers a new strategy for the selective and sensitive determination of tire rubber-derived emerging pollutants. This strategy paves the way for the assessment of environmental fate and toxicological risk of emerging contaminants.