Fabrication of MOF-on-MOF composites by surfactant-assisted growth strategy for SPME of polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are a class of persistent organic pollutants with strong carcinogenicity and mutagenicity, which cause great harm to the environment and food. Herein, a composite (NH₂-MIL-88@PCN-224) was prepared through a guest PCN-224 in situ grown on the host NH₂-MIL-88 by a surfactant-assisted growth strategy, and successfully applied for solid-phase microextraction (SPME) of PAHs from milk samples. The prepared SPME coatings exhibited high extraction and adsorption capacity for PAHs due to their porous structure, ultra-large specific surface area, strong π-π stacking, hydrophobic interactions and size-matching effects. The SPME-GC-FID method based on NH₂-MIL-88@PCN-224 coated fibers has the significant advantages of wide linear range (1-200 ng mL^-1), low detection limit (0.003-0.020 ng mL^-1), high recoveries (92.15-106.64%) and good reproducibility. This work overcomes the lattice-matching limitation by adopting a surfactant-assisted growth strategy, which offers a new direction for the preparation of ultra-high-performance SPME coatings with extremely high extraction efficiency, exceptional thermal stability, and long service life, and greatly expands the variety of MOF SPME coatings.