Self-Assembling Hydrophilic Magnetic Covalent Organic Framework Nanospheres as a Novel Matrix for Phthalate Ester Recognition

The development of covalent organic framework (COF)-derived materials with additional functions and applications is highly desired. In this work, a unique COF-functionalized hydrophilic magnetic nanosphere (Fe3O4@PDA@TbBd) with Fe3O4 as a magnetic core, polydopamine (PDA) as a hydrophilic middle layer, and TbBd as an outer COF shell was facilely prepared as a novel hydrophilic platform for efficient detection of phthalic acid esters (PAEs). The resultant Fe3O4@PDA@TbBd nanosphere displayed strong magnetic response, high surface area, and good hydrophilicity. Accordingly, the newly synthesized COF exhibited great potential in phthalate analysis with a wide linearity (50–8000 ng/mL), good recovery (92.3–98.9%), a low limit of detection (0.0025–0.01 ng/mL), and a small relative standard deviation (for intraday less than 4.6% and for interday less than 6.8%). More excitingly, the new COF was applied to analyze nine PAEs in the human plasma sample. This work opens up new avenues for the development and application of functionalized COF-derived materials.