## 4 Application of Fe-MOF in Advanced Oxidation Processes
### Catalytic AOP  
Some examples of various Fe-MOFs synthesized for the application of Fenton-based processes are shown in Table 6. Until now, Fe-MOFs from the MIL family (such as MIL-100-Fe, MIL-88-Fe and MIL-53-Fe) have demonstrated great interest and potential as Fenton catalysts because of their ease of synthesis, large surface area and high chemical stability [157]. [PERSON] et al. [158] synthesized by the solvothermal process three types of MIL-88A-Fe with different morphologies (rod, spindle and diamond). They concluded that the catalyst morphology affected the efficiency of the Fenton-like process. Thus, using rod-MIL-88A-Fe (r-MIL-88A-Fe) as a catalyst, phenol could be completely removed by the Fenton process with degradation levels higher than other reported Fe-based such as MIL-53-Fe, MIL-88B-Fe and MIL-101-Fe [159]. This fact could be explained by the DFT calculation that suggested the hydroxyl radical was more easily generated due to a lower H\({}_{2}\)O\({}_{2}\) dissociated energy barrier. In addition, the high surface of rod configuration increased the phenol removal. Moreover, the r-MIL-88A-Fe performance should be reusable for practical applications. In this sense, only a slight decline in r-MIL-88A's activity was detected, which indicates that this catalyst is highly reusable. Among the studies shown in Table 6, it is highlighted the Fe-MOF (core/shell Fe@C nanocomposites) was synthesized via a green technology by the combination of a mechanochemical approach and carbonization under an inert atmosphere. In this study, [PERSON] et al. [136] included a trace of Pd by addition of Na\({}_{2}\)PdCl\({}_{4}\) into the Fe-MOF, determining a positive effect on the pH endurance, life of modified catalyst and reduction in the generation of iron sludge. In addition, catalysts were re-used after they were recovered from reaction mixtures in the successive runs to verify their stability and operational limitation. As a result of their high magnetization, the catalysts could easily be recovered under an external magnetic field, showing a high level of phenol degradation decreasing around 70% after several cycles. This reduction in efficiency could be due to the metals leaching; however, there was a low and constant concentration (lower than 3 mg/L) of Fe and no Pd ions were present in the different cycles. These results suggest that the catalyst's life was extended, and metal sludge was reduced, thereby enabling the discharge of treated effluents directly into the environment. Figure 7: Keywords and overlay visualization co-occurrence analysis of AOPs using MOFs in wastewater research using VOS Viewer®. Fe@MesoC is another magnetic catalyst that has been synthesized from MIL-100-Fe by the pyrolysis/carbonization method and used as a catalyst in the Fenton process by degrading sulfamethoxazole (SMX) [160]. Similarly, the direct thermal treatment of MOFs holds great promise for constructing various metal oxide nanoparticles encapsulated inside porous carbon matrixes, providing compositions and structures tailored to the treatment's needs. As is shown in Table 6, the complete decomposing of SMX was achieved after two hours with only around 55% of total organic carbon removal. It could be due to the amelioration of the mesoporous carbon matrix or the abundance of active iron sites in the nanoparticles that this outstanding performance is possible. In addition, the electrons transfer from Fe\({}^{0}\) to iron oxide could enhance the reduction of ferric to ferrous iron anchored to the surface of the catalyst (\(\equiv\)Fe\({}^{3+}\) to \(\equiv\)Fe\({}^{2+}\), respectively) facilitating the redox cycle and the hydroxyl radical production. Recently, the bimetallic MOFs have been probed as Fenton-like catalysts. Thus, [PERSON] et al. [161] synthesized a bimetallic MOF, named Fe\({}_{x}\)Cu\({}_{1-x}\)(BDC), by the solvothermal method explained in Section 3.1. In this case, the DMF solution contained FeCl\({}_{3}\)\(\cdot\)6H\({}_{2}\)O, Cu(NO\({}_{3}\))\({}_{2}\)\(\cdot\)3H\({}_{2}\)O and H\({}_{2}\)BDC.