The practical applications of moisture sensitive metal-organic frameworks (MOFs) in the extraction technique are faced with avoided challenges related to competitive adsorption and hydrostability. The target analytes cannot be effectively extracted under humid conditions because of the competitive moisture adsorption and/or framework structure collapse of MOFs. In this Letter, metal-organic framework (MOF)@microporous organic network (MON) hybrid materials were explored for the first time as fiber coatings for solid-phase microextraction (SPME). Microporous materials with a hydrophobic surface was formed by coating the MOFs (MIL-101 and MOF-5) with MON through a sonogashira coupling reaction. MON acted as a hydrophobic "shield" to hinder the competitive moisture adsorption and improve moisture resistance and stability of the fiber. The sorbent exhibited higher enrichment factors (1215-3805) toward PAHs than other analytes in the water samples. An SPME method using MOF@MON-based fiber was developed to quantitatively determine PAHs. The proposed method was successfully applied to analyze PAHs in environmental water, particulate matter (PM), and food samples. A successful technique is proposed to chemically control MOF for applications in solid-phase sorption-based extraction techniques.

The presence of per- and poly-fluoroalkyl substances (PFASs) even at trace levels poses a potential threat to ecological safety and human health. PFASs often require an extraction pretreatment for enrichment before detection and analysis, which is still challenged by the relatively low efficiency because of the limited specific interactions involved. Here, we deliberately introduced multiple interactions into the solid-phase microextraction (SPME) process via a dual-functional modification of MIL-101­(Cr), i.e., amination and subsequent fluorination, which is then used as an adsorbent for the efficient enrichment of PFASs. In combination with ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS), ultrasensitive quantitative analysis is available for nine selected PFASs with high linearities above 0.9941 in the ranges of 0.5–1500 ng/L, low limits of detection of 0.004–0.12 ng/L, satisfactory repeatability and reproducibility with a relative standard deviation (RSD) < 11.6%, as well as excellent performance in complicated real water samples (recovery ratio of 76.2–108.6%). This work represents a rational design of a solid extractant with the desired structure and functionality for the selective enrichment and analysis of PFASs at trace concentrations in real applications.

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