## 3 Fe-MOF Synthesis
### Electrochemical Synthesis  
Regarding this type of synthesis, it is considered contrary to the solvothermal method, since it does not use high pressures and temperatures which are associated with high energy requirements, but rather operates under ambient conditions [108]. By using this synthesis method, the metal ion is provided through anodic dissolution in a synthesis mixture that includes organic linkers and electrolytes [109]. To carry out this synthesis, the following components are needed: an anode, a power supply and cathode plates. Normally, the assembly is very simple and does not require anything specific as it is only necessary that the anode and cathode are immersed in an electrochemical medium, in which both the metal salt and the organic ligands are included [110]. To clarify the idea of this synthesis method, Figure 4c shows a schematic representation of the general procedure followed. Therefore, in electrochemical synthesis, the most important parameters for MOF synthesis are the solvent, the applied voltage, the electrolyte and the temperature at which the synthesis is carried out. Similarly to microwave synthesis, this synthesis also takes a short amount of time [111], but unlike the others, it is the alternative that best solves the continuous production of these catalysts. In general, this type of synthesis method has attracted more interest because it provides the ability to synthesize MOF thin films or MOF-coated electrodes. This can \begin{table}
\begin{tabular}{c c c c c c} \hline
**MOF** & **Organic Ligand** & **Metal Source** & **Solvent** & **Procedure** & **Reference** \\ \hline \hline \multirow{8}{*}{MIL-100(Fe)/rGO} & \multirow{8}{*}{H\({}_{3}\)BTC} & & & Fe(NO\({}_{3}\))\({}_{3}\)-9H\({}_{2}\)O (14.43 g) and & \multirow{8}{*}{Water} & \multirow{8}{*}{[103]} \\  & & & & H\({}_{3}\)BTC (50.4 g) were dissolved in & & \\  & & & & water (36 mL). The rGO (50 mg) & & \\  & & & & was dispersed in distilled water & (100 mL) under ultrasonication & \\  & & & & for 1 h, and both dissolutions & & \\  & & & & were mixed for 1 h. Then it was & & \\  & & & & transferred to a Teflon-lined & & \\  & & & & stainless-steel autoclave (150 °C & \\  & & & & for 15 h). After that, the product & & \\  & & & & was collected, washed and dried & & \\  & & & & at 90 °C overnight. & & \\ \hline \hline \multirow{8}{*}{Cu-doped MIL-101(Fe)} & \multirow{8}{*}{H\({}_{2}\)BDC} & \multirow{8}{*}{FeCl\({}_{3}\)-6H\({}_{2}\)O and Cu(OAc)\({}_{2}\)} & \multirow{8}{*}{DMF} & A total of 1.35 g of FeCl\({}_{3}\) 6H\({}_{2}\)O, & \multirow{8}{*}{415 mg of Co(OAc)\({}_{2}\) were added to 30 mL of & \\  & & & & & DMF. Then it was transferred to a & \\ \cline{1-1}  & & & & Teflon-lined autoclave and left at & \\ \cline{1-1}  & & & & 110 °C for 20 h with a heating rate & \\ \cline{1-1}  & & & & of 5 °C/min. After the reaction & \\ \cline{1-1}  & & & & was over, the solid product was & \\ \cline{1-1}  & & & & collected, washed and dried at & \\ \cline{1-1}  & & & & 80 °C overnight. & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: _Cont._occur if the desired substrate is deposited directly or indirectly on that surface. Thus, this allows the adjustment of the MOF structure and control of the MOF characteristics. Taking this into account, direct and indirect electrosynthesis must be differentiated [112]. The main difference between both of them is that in the indirect methods the electrochemical process is carried out in a single step in the overall procedure of MOF synthesis, while in direct synthesis, this catalyst has already been obtained with only this electrochemical process [113]. Briefly, in direct synthesis, anodic dissolution and reductive electrosynthesis stand out, while in indirect synthesis, bipolar electrosynthesis, electrophoretic deposition and galvanic displacement stand out [112].