## 2 Cu-Based Catalyst-Activated PMS Processes
### Cu-Based Designed Catalyst Materials
#### 2.4.2 Cu-Based LDHs  
Regarding LDHs, these materials are two-dimensional compounds consisting of positively charged metal layers and charge-compensating anions located in the interlayer [121]. They can be represented by the general formula \(\left[M_{(1-x)}^{+2}M_{x}^{+3}(OH)_{2}\right]^{x+}\)\((A^{n-})_{x/n}\bullet\)m\(\cdot\)H\({}_{2}\)O, where M\({}^{+2}\) is a divalent cation, M\({}^{+3}\) is a trivalent cation, A\({}^{n-}\) is the intercalated anion with valence \(n\), and \(x\) (the molar ratio of M\({}^{+3}\) to (M\({}^{+2}\) + M\({}^{+3}\))) typically ranges from 0.2 to 0.4 for structural stability [122]. In Cu-based LDHs, the presence of low-valent Cu\({}^{+}\) species within the LDH structure can facilitate electron transfer on the catalyst surface, accelerating the activation of active species. For the synthesis of Cu-LDHs, several methods discussed in previous sections are employed, with particular emphasis on the solvothermal and MW methods. However, the most widely used synthesis process is coprecipitation, which is the method employed in all the studies described below and in Table 2. Coprecipitation synthesis involves mixing metal salts, controlling the temperature of the mixture, and adding a precipitating agent, typically a base like NaOH, to adjust the pH conditions. This method facilities the easy incorporation of different cations and anions, which is essential for tailoring the properties of LDHs to specific applications. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Catalyst** & **Contaminant** & **Reactive Species** & **Efficiency and Reusability** & **Ref.** \\ \hline \multirow{6}{*}{HKUST-1} & _Saccharomyces cerevisiae_ & & & \\  & (\(>\)10\({}^{5}\) CFU\(\cdot\)mL\({}^{-1}\)) & & 100\% in 25 h & [123] \\  & _Geotrichum candidium_ & & \(>\)79\% in 25 h & [123] \\  & (\(>\)10\({}^{5}\) CFU\(\cdot\)mL\({}^{-1}\)) & & & \\ \hline \multirow{2}{*}{HKUST-1} & _E. coli_ & & & \\  & (10\({}^{10}\) CFU\(\cdot\)mL\({}^{-1}\)) & \(SO_{4}^{\bullet-}\), \(HO^{\bullet}\) & 100\% in 30 min & [124] \\ \hline \multirow{2}{*}{FeCu-MOF} & Methylene blue & & & \\  & (0.2 mM) & \(SO_{4}^{\bullet-}\) & 100\% in 30 min & \\  & (0.2 mM) & \(SO_{4}^{\bullet-}\) & 3 cycles, 87.1\% & [125] \\ \hline \multirow{2}{*}{CuCo-MOF} & Nimesulide & & & \\  & (20 mg\(\cdot\)L\({}^{-1}\)) & \(SO_{4}^{\bullet-}\), \(HO^{\bullet}\) & 100\% in 25 min & [126] \\ \hline \multirow{2}{*}{CuCo-MOF-74} & Methylene blue & & & \\  & (0.2 mM) & \(SO_{4}^{\bullet-}\) & 100\% in 30 min & \\  & (0.2 mM) & \(SO_{4}^{\bullet-}\) & 5 cycles, 76.4\% & [116] \\ \hline \multirow{2}{*}{Co1 Cu1-MOF} & Tetracycline & \(SO_{4}^{\bullet-}\), \(HO^{\bullet}\) & 98.17\% in 30 min & \\  & (20 mg\(\cdot\)L\({}^{-1}\)) & \({}^{1}O_{2}\), \(O_{2}^{\bullet-}\) & 4 cycles, 71.26\% & [101] \\ \hline \multirow{2}{*}{NH\({}_{2}\)–Fe\({}_{2,4}\)Cu\({}_{1}\)-MOF in polyacrylamide spheres} & RhB & & & \\  & (10 mg\(\cdot\)L\({}^{-1}\)) & \(SO_{4}^{\bullet-}\), \(HO^{\bullet}\) & 80.92\% in 90 min & \\ \hline \multirow{2}{*}{NH\({}_{2}\)–Fe\({}_{2,4}\)Cu\({}_{1}\)-MOF in polyacrylamide spheres} & \multirow{2}{*}{[127]} & \multirow{2}{*}{[128]} & \multirow{2}{*}{[129]} & \multirow{2}{*}{[127]} \\  & (10 mg\(\cdot\)L\({}^{-1}\)) & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Cu-based designed catalysts for the degradation of organic pollutants and disinfection by PMS activation. The coprecipitation process is typically carried out under controlled pH conditions to ensure the formation of lamellar metal hydroxides. The concentration of metal salts, the rate of addition of the precipitating agent, and the reaction temperature are critical parameters that influence the final structure and properties of the Cu-LDH. The main advantage of coprecipitation is its simplicity and the ability to produce large quantities of material with uniformity. Unlike the MOFs described in Section 2.4.1, LDHs are usually bimetallic and even trimetallic, meaning they can incorporate two or three different types of metal cations into their structure.