## 2 Results and Discussion
### Ethylbenzene Oxidation
This is most likely due to the poor solubility of CoCl\({}_{2}\) and [emim][OcoSO\({}_{3}\)] in the ethylbenzene reagent, and the resulting formation of a separate IL phase, which was observed in the CoCl\({}_{2}\)/[emim][OcoSO\({}_{3}\)]-catalyzed reaction. The ionic liquid can partially dissolve CoCl\({}_{2}\), which is poorly soluble in ethylbenzene, thus hindering the contact between the reaction products (including hydroperoxide) and the active centers of PS-NHPI-4, as indicated by the decrease in its ethylbenzene conversion compared to the PS-NHPI-4/CoCl\({}_{2}\) system. The higher selectivities toward acetophenone production observed for the SCILL/SILP systems may also result from a solvent \"cage\" effect. The ionic liquid, which acts as a solvent, surrounds the alkoxy radical (Ph-CH(O-)-CH\({}_{3}\)) formed in the reaction and limits the possibility of its exit from the \"cage\" to react with ethylbenzene to form 1-phenylethanol. At the same time, this phenomenon favors the reaction to cleave the alkoxy radical into a ketone. For example, studies on the influence of the solvent properties on the initiation efficiency have shown that a solvent with higher viscosity provides less opportunity for radicals to leave the \"cage\", which lowers the initiator efficiency [43]. Like most ionic liquids, [emim][OcoSO\({}_{3}\)] is characterized by a higher viscosity than classic organic solvents [44], therefore the \"cage\" effect may influence the course of the reaction. Reuse of both the PS-NHPI/CoCl\({}_{2}\) and PS-NHPI@CoCl\({}_{2}\)@[emim][OcoSO\({}_{3}\)] catalytic systems were attempted, such that, after the completion of the ethylbenzene oxidation process, the reaction mixture was decanted and the catalyst was washed with hexane and dried. Then, a fresh batch of ethylbenzene and new AIBN were introduced. The results obtained over at least 3 reaction cycles are summarized in Table 4.  
Attempts to recycle the PS-NHPI/CoCl\({}_{2}\) systems (Table 4, entries 1-16) revealed that their activity gradually decreases in subsequent cycles, with the slowest decrease occurring in the case of PS-NHPI-5. As a result, in the 3 rd reaction cycle using PS-NHPI-2/CoCl\({}_{2}\), PS-NHPI-3/CoCl\({}_{2}\), and PS-NHPI-4/CoCl\({}_{2}\), and in the 4 th cycle using PS-NHPI-5/CoCl\({}_{2}\), these systems achieve an overall conversion similar to that obtained by PS-NHPI-4 alone in its first cycle (5.1%; shown for comparison in entry 33). The observed decrease in activity was likely related to the gradual removal of CoCl\({}_{2}\) (which was no physically bound to the PS-NHPI) with the reaction products. Despite the poor solubility of CoCl\({}_{2}\) in ethylbenzene, the polarity of the organic phase increased as the reaction progressed due to the generation of polar products, which suggests that some of the CoCl\({}_{2}\) was dissolved in the organic phase during the reaction, and then was decanted during the separation of the catalyst. As a result, the concentration of CoCl\({}_{2}\) was lower and lower in each subsequent reaction cycle. This concept is supported by the observed concomitant increase in selectivities toward ethylbenzene hydroperoxide, because the Co(II) compounds would otherwise accelerate the decomposition of the EBOOH to AP and PEOH. Comparative analysis of the course of the ethylbenzene oxidation reaction, as carried out by the PS-NHPI-4/CoCl\({}_{2}\) system in three consecutive reaction cycles, showed that the activity of reused PS-NHPI-4/CoCl\({}_{2}\) (i.e., in the 2 nd and 3 rd cycles) was similar to PS-NHPI-4 alone in the 1 st cycle (Figure 5). Another important aspect to consider in the analysis is the stability of the various PS-NHPI catalyst systems. The ester bond formed between the NHPI catalyst and the support can be decomposed. Comparing the FT-IR spectra (Figure 6) of the PS-NHPI-2 catalyst before the reaction to the PS-NHPI-2/CoCl\({}_{2}\) system after the 3 rd reaction cycle confirms the stability of the catalyst.