## 3 Results
### Heterogeneous Photocatalysis  
#### 3.3.1 Basolite F300 (MOF)  
Preliminary Study  
Initially, a simple photocatalytic experiment on the Nile Blue dye in the presence of Basolite F300 was carried out in order to evaluate the catalyst's efficiency. Prior to illumination, the dye solution was kept in the dark with the catalyst in order to assess its absorbance on the catalyst's surface. A 15.4% removal was recorded in the dark and, subsequently, the lamp was turned on and the photocatalytic degradation of the dye was monitored. The results are demonstrated in Figure 7.  
As can be observed, the degradation of the Nile blue dye proceeds very slowly in the presence of the MOF catalyst, achieving only a 6.3% reduction after one hour of irradiation. The slow rate of dye degradation can be attributed to the rapid recombination of photogenerated holes and electrons [34]. All experiments with Basolite F300 were conducted at a neutral pH without additional acidification. Effect of H\({}_{2}\)O\({}_{2}\) Concentration  
Due to the slow rate of dye decomposition by simple photocatalysis in the presence of the Basolite F300 catalyst, the experiments were performed with oxidant addition, so as to achieve the following:  
To limit the hole-electron recombination. To produce additional active radicals from self-activation of the oxidant by radiation. To achieve, apart from the heterogeneous photocatalytic process, a photo-Fenton reaction, as the catalyst is an iron-based MOF. Figure 7 presents the photocatalytic degradation of the target compound in the presence of four different H\({}_{2}\)O\({}_{2}\) concentrations (100, 200, 300, and 500 mg L\({}^{-1}\)) and the Basolite F300 catalyst. The addition of the oxidant clearly enhances the photocatalytic degradation of the dye. Furthermore, the degradation rate increases with an increasing H\({}_{2}\)O\({}_{2}\) concentration up to 200 mg L\({}^{-1}\). However, beyond this concentration, a decline in the degradation rate is observed. As mentioned before, this may be due to the action of hydrogen peroxide as a scavenger of hydroxyl radicals, as already mentioned in Equations (6)-(8). In order to evaluate if a synergistic effect takes place, meaning that the combination of the catalyst and the oxidant results in a greater performance than the sum of the contributions of the standalone systems [38], the following equation is used:  
\[ \begin{array}{c}\text{\%{\emph{removal by Basolite F300}}}/H_{2}O_{2}\\ \text{\%{\emph{removal by Basolite F300}}}+\text{\%{\emph{removal by H${}_{2}$O }}}=\frac{60.68}{6.32+20.69}\%=2.25>1\end{array} \]  
The resulting value significantly exceeding unity (2.25 \(>\) 1) clearly indicates the presence of a synergistic effect. This suggests that the combined system of Basolite F300 and H\({}_{2}\)O\({}_{2}\) does not merely add their individual efficiencies, but they rather interact in a way that amplifies the overall photocatalytic degradation of the dye. Such a synergistic interaction can be attributed to the enhanced generation of reactive species, improved electron-hole separation, or the catalytic activation of H2O2 by Basolite F300, all of which contribute to the markedly improved performance observed. Effect of S2O82- Concentration  
Accordingly, in order to study the effect of the K2S2O8 oxidant on the photocatalytic degradation of the studied dye with the Basolite F300 catalyst, experiments were also carried out with four different concentrations of S2O82- (100, 200, 300, and 500 mg L-1). The results are presented in Figure 8.  
As observed, the addition of the oxidant strongly enhances the degradation of the target compound. An increase in the concentration of persulfate also causes the enhancement of the degradation rate up to 300 mg L-1. Above the optimum concentration, scavenging effects may occur, reducing the reaction rate.