Size–controllable synthesis of moderate–sized spherical 2D covalent organic frameworks for enrichment of bisphenol F

Synthesis of moderate–sized uniform spherical covalent organic frameworks (COFs) within 10–50 μm is crucial for their applications in separation fields, while the spherical 2D COFs with such particle sizes has not been reported till now. Herein, a type of moderate–sized spherical 2D COF (TFB–BD COF) with uniform size within 10–50 μm was size–controllably synthesized via an ‘emulsion polymerization–crystallization’ strategy. The obtained TFB–BD COF showed monodisperse full–spherical morphology, good crystal structure and uniform controllable particle sizes. Moreover, another spherical 2D COF (TAPT–PDA COF) with particle size of 15 μm was also synthesized through a similar method for investigating the application potential of the spherical 2D COFs. As an application case, the spherical TAPT–PDA COF was used as the adsorbent for the disperse solid–phase extraction (d–SPE) of bisphenol F (BPF). The adsorbent showed good adsorption selectivity, high adsorption capacity, fast binding kinetics, good reusability (at least four cycles) and high enrichment factor (60 folds). By combining this d–SPE technique with high–performance liquid chromatography, a new analytical method was established for determination of trace BPF in water samples and an orange juice with recoveries of 94.8–101.6% and LOD of 0.56 ng/mL. The synthesis strategy proposed in this work opens a way for size–controllably synthesizing moderate–sized spherical 2D COFs, and the developed analytical method provides a viable path for detecting trace BPF in water samples and beverages.