# Supramolecular Materials as Solid-Phase Microextraction Coatings in Environmental Analysis
## 4 Covalent Organic Frameworks (COFs)
### COFs as SPME Coatings for Environmental Applications
#### 4.3.4 Extraction of Pesticides and Insecticides from Water Samples
The COF was synthesized based on a cycloaddition approach using TPB and 2,5-dimethoxyyterephthalalaldehyde as building blocks, followed by post-synthetic functionalization using 4-ethynylbenzonitrile. The SPME coating was fabricated by a two-step deposition using a PDMS layer for the physical deposition of the COF. Although post-synthetic functionalization led to a reduction in both the BET surface and pore volume of the material (700 m\({}^{2}\)/g and 1.2 nm for the COF-CN vs. 1983 m\({}^{2}\)/g and 2.5 for the unfunctionalized COF), the COF-CN material showed higher thermal stability and increased hydrophobicity. The developed COF exhibited EFs higher than commercially available coatings: values in the 540-5065 range were calculated, benefitting from suitable pore size, \(\pi\)-\(\pi\) stacking, and a larger specific surface area. The HS-SPME-GC-MS/MS method was validated for 14 OCPs, obtaining LOQs in the 0.0030-45.13 ng/L range andgood precision (RSDs \(<\) 12%). Finally, the validated method was applied for the determination of OCPs in water samples from various cities in Henan Province, detecting six OCPs in all samples, hexachlorobenzene and aldrin in all samples except one, and heptachlor and 4_A_'-DDT in some urban samples. Trace detection of insecticides is another key issue for environmental monitoring due to their worldwide use, high stability, and high toxicity, resulting in a strong impact on the aquatic ecosystems [127; 128]. [PERSON] et al. developed an SPME coating based on a trifluoromethyl-grafted COF named COF-(CF\({}_{3}\))\({}_{2}\) for the extraction of benzoylurea insecticides from water samples [127]. The COF scaffold was synthesized under solvothermal conditions using 2,5-Dibromoterephthalaldehyde and 1,3,5-tris(4-aminophenyl) benzene, post-synthetically functionalized through the Suzuki-Miyaura cross-coupling reaction under mild condition and deposited onto SS wires using a silicone glue. Although the functionalization with the trifluoromethyl group decreased both the BET surface and pore size from 1991 m\({}^{2}\)/g to 1636 m\({}^{2}\)/g and from 2.5 nm to 2.0 nm, respectively, a strong increase in the hydrophobicity as well as in the chemical and thermal stability was observed. The COF-(CF\({}_{3}\))\({}_{2}\) coating showed higher EFs (in the 44-105 range) compared to unfunctionalized COF and up to three times higher than those calculated using commercially available fibers, due to strong hydrogen bonds and fluorine-fluorine interactions between the COF coating and the analytes. In addition, hydrophobic, \(\pi\)-\(\pi\) stacking interactions, C-H \(\cdot\cdot\cdot\pi\) interactions, and C-F \(\cdot\cdot\cdot\pi\) interactions could be established. The DI-SPME-UHPLC-MS/MS method was validated, obtaining LOQs in the 0.20-1.70 ng/L range, recoveries in the 76.2-107.6% range, and good precision (RSDs \(\leq\) 11%). The method was applied for the analysis of wastewater, river, lake, pond, and farmland water: the insecticides were detected in all the samples except for river water, with concentrations up to 33.2 ng/L. Eleven pyrethnot insecticides were extracted by [PERSON] and coworkers using a sea-urchin-like COF (COF\({}_{\text{TDBA-TTL}}\)) [128]. The COF was synthesized under solvothermal conditions and deposited onto SS wires using a silicone adhesive. The coating interacted with the investigated pyrethnot insecticides through electrostatic, hydrophobic, and \(\pi\)-\(\pi\) interactions, and hydrogen bonding, showing extraction performance up to 446 times higher than commercially available coatings. The DI-SPME-GC-MS method was validated, obtaining LOQs in the 0.720-5.61 ng/L range, EFs in the 2584-7199 range, and RSDs \(\leq\) 13%. Finally, tefluthrin, cyhalothrin, acrinathrin, permethrin, and etoferprox were detected in Pearl River water samples at a concentration of 7.54, 9.96, 7.70, 10.3, 17.2, and 11.0 ng/L, respectively.