## 2 Results and Discussion
### Ethylbenzene Oxidation
The obtained results suggest significantly limited elution of CoCl\({}_{2}\) from the IL layer,  
Figure 5: The course of ethylbenzene oxidation with dioxygen in the presence of PS-NHPI-4 and the PS-NHPI-4/CoCl\({}_{2}\) system reused in three successive reaction cycles. Figure 6: FT-IR spectra of fresh PS-NHPI-2 (I) and PS-NHPI-2/CoCl\({}_{2}\) after the 3 rd cycle (II). which indicates greater potential for recycling and reusing SCILL/SILP systems. Analyzing the course of the ethylbenzene oxidation reaction carried out by the PS-NHPI-4@CoCl\({}_{2}\)@[emim][OCOSO\({}_{3}\)] system over three reaction cycles showed no significant differences in the oxidation rate during subsequent cycles (Figure 7). Comparison of the FT-IR spectra recorded for the PS-NHPI-4 and PS-NHPI-4@CoCl\({}_{2}\) @[emim][OCOSO\({}_{3}\)] catalysts before the reaction and for the PS-NHPI-4@CoCl\({}_{2}\)@[emim][OCOSO\({}_{3}\)] catalyst after the 3 rd reaction cycle is presented in Figure 8. As expected, the FT-IR spectrum of the PS-NHPI-4@CoCl\({}_{2}\)@[emim][OCOSO\({}_{3}\)] system has bands indicating the presence of PS-NHPI-4, including one characteristic of the OH group (v\({}_{\text{OH}}\)) at about 3449 cm-1 and one typical carbonyl stretching band (v\({}_{\text{C=O}}\)) at 1720 cm-1. The bands at about 1234 and 1573 cm-1 are evidence presence of the ionic liquid (see Figure S15). The very strong, broad band at around 1234 cm-1 presumably corresponds to also the ester stretching vibrations (v\({}_{\text{C-O}}\)) in PS-NHPI-4. The FT-IR spectrum of the PS-NHPI-4@CoCl\({}_{2}\)@[emim][OCOSO\({}_{3}\)] system acquired after the third reaction cycle contains bands confirming the presence of PS-NHPI-4, intensive of the hydroxyl group stretching vibration bands (v\({}_{\text{OH}}\)) at about 3243 cm-1 and the carbonyl stretching band (v\({}_{\text{C=O}}\)) at 1713 cm-1. The bands observed at 1574 and 1237 cm-1 indicate the presence of the ionic liquid (Figure S15), while the new, very strong band at 1086 cm-1 (v\({}_{\text{C-O}}\)) indicates that the PEOH (Figure S16) product was not completely washed off of the surface of the recycled catalyst. In order to unequivocally confirm the presence of the ionic liquid in the recycled PS-NHPI-4@CoCl\({}_{2}\) @[emim][OCOSO\({}_{3}\)], thermogravimetric analysis (TGA) was conducted (Figure 9) to compare the fresh PS-NHPI-4@CoCl\({}_{2}\)@[emim][OCOSO\({}_{3}\)] catalyst, with that which was separated after three reaction cycles. The analysis revealed that, in both cases, a weight loss of approx. 71% (from 95% to 24%) was observed over the temperature range from 200-500 \({}^{\circ}\)C. This confirms the presence of an ionic liquid on the catalyst surface and excludes the idea that the IL gets washed away during the catalyst recycling process. Therefore, we suppose that the slight decrease in the activity of the studied catalysts may be caused by the absorption of polar products in the IL layer. This may influence the activity of the catalytic system, e.g., by influencing the solubility of the substrate in the IL layer. Figure 7: The course of ethylbenzene oxidation with dioxygen in the presence of PS-NHPI-4@CoCl\({}_{2}\) @[emim][OCOSO\({}_{3}\)] over three reaction cycles, as compared to the 3 rd cycle using only PS-NHPI-4/CoCl\({}_{2}\). Figure 8: FT-IR spectra of PS-NHPI-4(**I**), PS-NHPI-4@CoCl\({}_{2}\)@[emim][OCOSO\({}_{3}\)] (as-prepared, before any oxidation reaction) (**II**), and PS-NHPI-4@CoCl\({}_{2}\)@[emim][OCOSO\({}_{3}\)] after the 3 rd reaction cycle (**III**). Figure 9: TGA curves obtained for fresh PS-NHPI-4@CoCl\({}_{2}\)@[emim][OCOSO\({}_{3}\)] and PS-NHPI-4@CoCl\({}_{2}\) @[emim][OCOSO\({}_{3}\)] after the 3 rd reaction cycle.