Hierarchically porous UiO-66-(OH)₂@COF-OMe composites with multiple binding sites for synergistic extraction of...

Selective enrichment of polybrominated diphenyl ethers (PBDEs) contamination within complex aqueous matrices is crucial for safeguarding water safety and ecosystem health. Herein, a novel dual-functionalized MOF@COF core-shell composite (UiO-66-(OH)₂@COF-OMe) was fabricated via a polymer-mediated interfacial engineering strategy, where the surface of a hydroxyl-functionalized MOF was first modified with polyethyleneimine (PEI) and polyvinylpyrrolidone (PVP) as interfacial bridges, followed by the formation of a methoxy-functionalized COF shell via interfacial assembly. The composite retains high surface area and the crystallinity of the parent materials while forming a hierarchically porous structure featuring hydroxyl groups and N/O-rich functionalities. Benefiting from the synergistic effect between its core-shell structure and multiple binding sites, UiO-66-(OH)₂@COF-OMe exhibits specific recognition and enhanced enrichment capability toward PBDEs. The prepared MOF@COF composite was employed as a fiber coating for solid-phase microextraction (SPME), effectively enriching PBDEs prior to GC-MS analysis and achieving high enrichment factors (1868-4272). The developed SPME-GC-MS method allows for the quantification of PBDEs in real water samples with a wider linear range (0.05-200 ng L^-1), lower limits of detection (0.0026-0.034 ng L^-1), and satisfactory recoveries (81.4%-116.1%). Both experimental and DFT computational results reveal that the enhanced adsorption performance originates from a multimodal synergistic mechanism, involving size-matching effects, hydrophobic interactions, π-π stacking, halogen bonding, and hydrogen bonding. This work presents a rational strategy that enables the targeted construction of dual-functionalized MOF@COF adsorbent and elucidates the underlying multimodal enrichment mechanism as well.