## 4 Application of Fe-MOF in Advanced Oxidation Processes
### Electrochemical AOP
#### 4.3.1 Electro-Fenton
Therefore, they concluded that the CMIL-100@PCM25 catalyst was the best because it could remove near complete the herbicide pollutant, napromide, in 1 h. Moreover, it could be used in three cycles practically without altering its herbicide removal capacity. Within this strategy, [PERSON] et al. [201] were able to fabricate a modified graphite(GF) electrode using a bimetallic MOF as a precursor, named Cu\({}_{0.33}\)Fe\({}_{0.67}\)NBDC-300/GF to degrade SMX. The main improvement achieved by synthesizing this electrode was that the regeneration of Fe\({}^{2+}\) was considerably accelerated due to the coexistence of the Fe\({}^{2+}\)/Fe\({}^{3+}\) and Cu\({}^{+}\)/Cu\({}^{2+}\) redox reactions. In addition, another improvement incorporated in the electro-Fenton process was that it favored the generation of more active radicals, such as OH\({}^{\bullet}\) (Equation (11)) and O\({}_{2}\)\({}^{-\bullet}\) (Equation (10)). These two radicals were suggested because, during the study of the generation of the radicals, they detected that up to 45 min the degradation of SMX was due to the free OH\({}^{\bullet}\) and the ones bound to the electrode surface. However, from 45 to 75 min, O\({}_{2}\)\({}^{-\bullet}\) was found to play an important role in the degradation. In fact, at 75 min, SMX was completely eliminated in a pH range of 4 to 9. As well as allowing it to operate in a wide pH range, it has high stability and can be used in several reuses; in this case, five cycles were made, without affecting its catalytic activity. The second strategy employed is the addition of suspended heterogeneous catalysts in the bulk solutions, as illustrated in Figure 10b. For this strategy, we can highlight the study performed by [PERSON] et al. [202], in which a MOF-engineered FeS\({}_{2}\)/C nanocomposite was synthesized. This catalyst was fabricated from a Fe-MOF precursor which they added sulfur and subjected it to carbonization and sulfidation, simultaneously. By operating in this mode, they produced well-dispersed FeS\({}_{2}\) pyrite nanoparticles, approximately 100 nm in diameter, bound to porous carbon. The reason for this synthesis was to solve the problem presented by pyrite, which, despite being an excellent donor and a catalyst with an outstanding performance in electro-Fenton processes, is not used due to its high iron leaching. Therefore, this FeS\({}_{2}\) nanocatalyst is intended to solve this problem and has similar properties that characterize pyrite. To study the catalytic capacity of the FeS\({}_{2}\)/C nanocatalyst in the electro-Fenton process, an anode of boron-doped diamond (BDD) was used and as a cathode, carbon cloth coated with carbon-polytetrelluoroethylene (PTFE), which is a type of electrode commercially available from BASF. Using this configuration, the system was optimized and it was established that the optimal operating conditions were a pH close to neutral, a current intensity of 50 mA and a catalyst load of 0.4 g/L, achieving a fluoxetine removal level of around 92% after 1 h. In addition, its reusability was also demonstrated. Based on this study, it was found that the catalyst retains its catalytic properties even after being reused five cycles; however, its catalytic properties were reduced as the number of cycles increased. In the fifth cycle, only 61% could be eliminated. Therefore, with the MOF-engineered FeS\({}_{2}\)/C nanocatalyst, it was possible to have the FeS\({}_{2}\) on the surface of the carbon and to solve the problem of pyrite reusability in the electro-Fenton process. Due to the possible self-decomposition of Fe-MOF in water, these authors also developed a heterogeneous electro-Fenton process using as catalyst magnetic MIL(Fe)-type MOF-derived N-doped nano-ZVI@C rods synthesized by pyrolysis of MIL-88B and NH\({}_{2}\)-MIL(Fe)-88 in an inert atmosphere at 800 \({}^{\circ}\)C [203]. This final step induced the carbonization of organic polymers, resulting in highly porous carbon with magnetic properties transforming the metal MOF into magnetic nanosized MOF.