## 1 Introduction
Taking into account the promising results for the implementation of NHPI, it is worth developing this type of catalysts further, trying to immobilize NHPI functionalities on solid supports, thus moving from a homogeneous system to a technologically more favorable heterogeneous one. In such a case, a used catalyst would not have to be recovered by controlled evaporation of a solvent combined with precipitation, which significantly increases operating costs. Immobilization of NHPI on a surface of poly(2-hydroxythacrylate) [20], cross-linked aminoethylstyrene, chloroethylstyrene [21; 22], copolymer of styrene, and maleic anhydride [21], as well as copolymer of glycidyl methacrylate, diethyl glycol dimethacrylate, and methyl methacrylate [23] was described. It was shown that the deposition did not significantly affect the activity of NHPI in the process of aerobic oxidation of p-methoxytoluene, \(\alpha\)-methylstyrene, cyclohexane, or acetophenone, respectively. [PERSON] et al. [24] developed a catalyst by immobilizing an NHPI precursor on commercial cross-linked polystyrene using the Friedel-Crafts reaction. In the oxidation of 1-phenylethanol with the use of VO(acac)\({}_{2}\) as a cocatalyst, acetophenone was obtained as the only product with the yield of \(\sim\)40%. Another approach to the synthesis of NHPI-based catalysts for oxidizing alcohols to corresponding ketones was to obtain a derivative that could be attached to ionic liquids, as described by [PERSON] et al. [25]. [PERSON] et al. [26] used immobilized NHPI for the synthesis of complex O-alkyl hydroxamines. The method was based on the reaction of trimellitic chloride and NHPI precursor with aminomethyl polystyrene resin and the subsequent reaction with hydroxylamine hydrochloride. In turn, [PERSON] et al. [27] reacted trimellitic anhydride with O-para-methoxybenzylhydroxylamine hydrochloride, and then deposited the obtained product on aminomethyl polystyrene resin. In the last stage of the synthesis, catalytically active NHPI moieties were obtained in the reaction with hydroxylamine hydrochloride. A NHPI precursor was similarly deposited on commercial polystyrene resins (i.e., aminomethyl and chloromethyl), as well as chloromethylated copolymer of styrene and divinylbenzene [28]. NHPI species were immobilized on various solid supports, including silicas [29; 30; 31; 32], zeolites [33], MOFs [34], diamond particles [35] or carbon nanotubes [36]. An interesting approach to anchoring NHPI groups on the surface of mesoporous silica was described by [PERSON] et al. [37]. The \(N\),\(N\)-dihydroxypyromellitimide (NDHPI) was attached to 3-glycidyloxypropyltrimethoxysilane (GPTMS), and the resulting organosilane precursor was grafted on the surface of SBA-15. The synthesized catalyst gave toluene conversion of 14.8% at temperature of 90 \({}^{\circ}\)C under 1.6 MPa of O\({}_{2}\). GPTMS was used as the linking molecule to graft NHPI onto the surface of commercial SiO\({}_{2}\)[38; 39]. In addition, NHPI was studied in photocatalytic [40; 41] and electrocatalytic selective oxidation [42; 43], aerobic dehydrogenation of \(N\)-heterocycles [44], and intermolecular anti-Markovnikov hydroamination of alkenes [45]. The developed strategies of grafting of NHPI precursors onto available polymeric substrates are based on using a variety of linkers that provide amide or ester bondings. Unfortunately, the formed connections are unstable since the immobilized groups exposed to catalytic reaction conditions are relatively easily hydrolyzed. As a result, detachment of functional groups and migration of NHPI molecules into the reaction environment may occur. Conducting the oxidation processes in the presence of such prepared NHPI-deposited catalysts is therefore associated with strict limitations. In our previous paper [46], permanently anchoring NHPI groups in the copolymer structure was demonstrated.