## 3 Fe-MOF Synthesis
### Microwave-Assisted Synthesis  
In general, microwave-assisted synthesis is based on the alignment of the dipoles of the material in an external field through the excitation produced by microwave electromagnetic radiation [92]. In addition, it has great characteristics compared to other MOF synthesis techniques: it is one of the fastest processes since the crystal nucleation is very fast; its heating is homogeneously distributed and it is environmentally sustainable [93; 94; 95]. Moreover, due to the type of heating and the short reaction times, it obtains more uniform crystalline particles with a larger surface area. It should be noted that it is easier to control the sizes of the crystals synthesized by this method, they are more repeatable, have a higher percentage yield in production and require smaller volumes of solvent to obtain them [96]. In this Table 5, some examples of Fe-MOF syntheses are given to show how to proceed. As can be seen in Figure 4b, as in solvothermal synthesis, the reagents are first mixed, then incorporated into the reactor and subjected to certain conditions of temperature, time and power of the microwave equipment. The last step is purification to obtain the synthesized catalyst. With this general idea of the process, it should be noted that the Fe-MOFs found in the literature have been mostly unmodified MOFs, as in the work of [PERSON] et al. [97] or with functionalisation of the amino group, as in the work of [PERSON] et al. [98]. \begin{table}
\begin{tabular}{c c c c c c} \hline
**MOF** & **Organic Ligand** & **Metal Source** & **Solvent** & **Procedure** & **Reference** \\ \hline \multirow{4}{*}{MIL-100-1} & \multirow{4}{*}{\begin{tabular}{c} Trimseic acid \\ (H\({}_{3}\)BTC) \\ \end{tabular} } & \multirow{4}{*}{FeCl\({}_{3}\)} & \multirow{4}{*}{Water} & H\({}_{3}\)BTC and FeCl\({}_{3}\) (molar ratio 1:1) & \multirow{4}{*}{[90]} \\  & & & & were mixed and transfer in a & \\  & & & & Teflon autoclave and placed in an & \\  & & & & oven (200 \({}^{\circ}\)C, 8 h). After cooling & \\  & & & & at room temperature, it was & \\  & & & & purified and dried at 80 \({}^{\circ}\)C under & \\  & & & & a vacuum overnight & \\ \hline \multirow{4}{*}{MIL-100-2} & \multirow{4}{*}{H\({}_{3}\)BTC} & \multirow{4}{*}{Fe(NO\({}_{3}\))\({}_{3}\)} & \multirow{4}{*}{Water} & H\({}_{3}\)BTC and Fe(NO\({}_{3}\))\({}_{3}\) (molar ratio 1:1) were mixed in water & \\  & & & & following the same procedure as & \\  & & & & MIL-100-1. & \\ \hline \multirow{4}{*}{MIL-100-3} & \multirow{4}{*}{H\({}_{3}\)BTC} & \multirow{4}{*}{Fe\({}_{2}\)(SO\({}_{4}\))\({}_{3}\)} & \multirow{4}{*}{Water} & H\({}_{3}\)BTC and Fe\({}_{2}\)(SO\({}_{4}\))\({}_{3}\) (molar ratio 1:1) were mixed in water & \\  & & & & following the same procedure as & \\  & & & & MIL-100-1. & \\ \hline \multirow{4}{*}{Fe/Co-MOF-x} & \multirow{4}{*}{\
\begin{tabular}{c} Terephthalatic acid \\ (BDC) \\ \end{tabular} } & \multirow{4}{*}{
\begin{tabular}{c} FeCl\({}_{3}\)-6H\({}_{2}\)O and \\ CoCl\({}_{2}\)-6H\({}_{2}\)O \\ \end{tabular} } & \multirow{4}{*}{DMF} & \multirow{4}{*}{[90]} \\  & & & & Metal ions (Fe\({}^{3+}\) and Co\({}^{2+}\)) and & \\  & & & & BDC were dissolved in DMF with & \\  & & & & a molar ratio of 1:1. Once NaOH & \\  & & & & solution was added, it was put in & \\  & & & & an oven at 100 \({}^{\circ}\)C for 10 h. When & \\  & & & & the reaction was completed, the & resulting solid was recovered, \\  & & & & cleaned and dried in a vacuum & \\  & & & & oven at 60 \({}^{\circ}\)C. & \\ \hline \end{tabular}
\end{table} 
Table 4: Examples of solvothermal/hydrothermal synthesis of Fe-MOF.