# Supramolecular Materials as Solid-Phase Microextraction Coatings in Environmental Analysis
## 3 Metal-Organic Frameworks
### MOFs as SPME Coatings for Environmental Applications
#### 3.3.7 Extraction of Other Compound Classes
UiO-66-NH\({}_{2}\) was obtained by solvothermal synthesis, dispersed in a solution containing phenolic resin precursors, and the composite resin/UiO-66-NH\({}_{2}\) material was synthesized by solvent-evaporation-induced self-assembly. Finally, Zr/N-OMC was obtained by carbonization of the composite and deposited onto SS wires using a neutral silicone sealant. Zr/N-OMC was characterized by faster equilibrium rates and a higher extraction efficiency compared to non-doped and N-doped OMC, despite the similar pore structure and lower BET surface (775, 720, and 583 \(\mathrm{m^{2}/g}\) for OMC, N-OMC, and Zr/N-OMC, respectively). Zr doping increased the adsorption rates and the extraction amounts of phenols, benefiting from Lewis acid-base interactions between the coating and the analytes. The hybrid coating was applied for the extraction of six model phenols from water samples and the HS-SPME-GC-MS method was validated, achieving LODs in the 0.21-1.7 \(\mathrm{ng/L}\) range, a three order of magnitude linear range, and a fiber-to-fiber precision with RSDS \(\leq\) 10%. The method was applied for the extraction of phenols from surface water: all the analytes except 2,4,6-trichloroophenol were detected in the 20.0(\(\pm\)1.0)-315.0(\(\pm\)10.0) and 20.0(\(\pm\)1.2)-330(\(\pm\)12.0) ranges in river and pond samples, respectively. UiO-66-NH\({}_{2}\) was also used to develop a new SPME coating that combines the extraction capability of MOF with ionic liquids (IL) [90]. The coating was deposited by treating the SS fibers with hydrofluoric acid and hydrogen peroxide to obtain hydroxyl groups for in situ MOF growth. The functionalization with the 1-hydroxyethyl-3-vinylimidazole chloride was performed in situ, exploiting the interaction between the anion and the zirconium modes (Figure 6); the final IL/MOF was used for the DI-SPME extraction of phthalate esters (PAEs) from water samples. Interestingly, the incorporation of the IL inside the MOF increased the hydrophobicity of the channels while promoting hydrogen bond formation and \(\pi\)-\(\pi\) interactions between the coating and the PAEs. The developed coating provided a higher extraction efficiency than commercial 100 \(\mathrm{\SIUnitSymbolMicro m}\) PDMS, 75 \(\mathrm{\SIUnitSymbolMicro m}\) CAR/PDMS, and 65 \(\mathrm{\SIUnitSymbolMicro m}\) PDMS/DVB fibers, and the non-ionic coating. Under optimal conditions, the validated DI-SPME-GC-MS method was showed by LOQs in the 0.6-1.2 \(\mathrm{ng/L}\) range, a three order of magnitude linearity, and precision, with RSDs \(\leq\) 12%. Finally, the method was tested for the extraction of PAEs from spiked surface and bottled water samples, obtaining good recoveries in the 90.3-102.4% range. Finally, an interesting study was carried out by [PERSON] and coworkers, who developed an aptamer-functionalized MOF (PAN/UiO@UiO2-N3-aptamer), based on the UiO-66-NH\({}_{2}\) structure [91], for the selective LC-MS recognition of Microcystin-LR at trace levels. The UiO-66-NH\({}_{2}\) seed crystals were prepared using solvothermal conditions and electrospun with PAN to obtain a PAN/UiO SPME coating. The MOF was grown in situ by a seeding procedure and functionalized to obtain the azide intermediate to be used as binding site for the aptamer. The specific affinity recognition of the material toward the target analyte was demonstrated by comparing the performance of the PAN/UiO@UiO2-N3-aptamer with that of the intermediate materials and the MOF functionalized with a control oligonucleotide for the extraction of Microcystin-LR in the presence of two different structural analogs. The results highlighted the superior performance of the PAN/UiO@UiO2-N3-aptamer coating, characterized by a high extraction capability, selectivity, and recovery up to 95.2%. By contrast, no significant difference in terms of adsorption capability was observed when the other materials were used, thus indicating that non-specific interactions were responsible for the adsorption of the compounds.