## 2 Cu-Based Catalyst-Activated PMS Processes
### Cu-Based Designed Catalyst Materials
#### 2.4.1 Cu-Based MOFs
For example, the combination of the MW-assisted and solvothermal methods can result in a hierarchical porous structure that provides a larger specific surface area, better thermal and chemical stability, and increased adsorption capacity [111]. In relation to the applicability of Cu-MOFs as catalysts for PMS, the literature reports several examples such as those summarized in Table 2. For example, an ultra-thin Cu-TCPP(BA)-MOF synthesized by [PERSON] et al. [112] exhibits high efficiency in PMS activation under visible light, completely degrading 10 ppm of RhB in 40 min through the non-radical species \({}^{1}\)O\({}_{2}\)[112]. The generation of \({}^{1}\)O\({}_{2}\) and \(HO^{\bullet}\) radicals is attributed to the Cu-TCPP(BA)-MOF transitioning from Cu(I) to Cu(II) when irradiated with visible light, producing h\({}^{+}\). This process, in reaction with the \(HSO_{5}^{-}\), triggers multiple reactions that result in the formation of superoxide, hydrogen peroxide, and \(SO_{5}^{\bullet-}\), leading to a significant production of \({}^{1}\)O\({}_{2}\). Additionally, this system can eliminate various organic pollutants such as tetracycline and phenol under conditions of 0.1 g\(\cdot\)L\({}^{-1}\) of PMS and 0.1 g\(\cdot\)L\({}^{-1}\) of catalyst at neutral pH. It also effectively inactivates pathogens such as _Escherichia coli_ (_E. coli_), achieving the complete inactivation of 10\({}^{7}\) colony-forming units per mL (CFU\(\cdot\)mL\({}^{-1}\)) in just 50 min. Moreover, some Cu-MOFs for the activation of the PMS can follow other pathways such as the generation of \(SO_{4}^{\bullet-}\) and \(HO^{\bullet}\) radicals. One example is the Cu-MOF modified with Fe\({}^{+3}\) ions synthesized by [PERSON] et al. [113], which improved degradation efficiency due to the increased ion exchange within the MOF and the reduction of coordinatedwater molecules thanks to the presence of this ion. Modification with different long-chain quaternary ammonium bromides established a hydrophobic microenvironment, favoring the removal of non-steroidal anti-inflammatory drugs such as diclofenac, NPX, and ibuprofen. The best PMS activation was achieved with the MOF modified with hexadecyltrimethylammonium bromide, achieving a 90% removal of diclofenac in 120 min. However, the removal of other non-steroidal anti-inflammatory drugs, such as ibuprofen and NPX, did not exceed 30%. Although it was not efficient for other drugs of the same class, it showed high stability, with only a 20% reduction in activation after five cycles, demonstrating high durability and reusability, and it was effective in complex waters such as tap water and secondary effluent water. In pursuit of enhancing the stability and usability of Cu-MOFs, Cu-MOF-74 stands out, as synthesized by [PERSON] et al. [114] through a green synthesis method on a PVDF membrane, resulting in a catalytic membrane reactor. This reactor demonstrated the ability to activate PMS and achieve the complete removal of RhB in 60 min while also efficiently removing other compounds such as methylene blue (89.5%), tetracycline (67.9%), and rifampicin (80.9%). Additionally, in recent years, new structures have been sought to generate new MOFs. [PERSON] et al. synthesized the MOF [Cu\({}_{3}\)(\(\mu_{3}\)-O)(pypz)\({}_{3}\)]NO\({}_{3}\), which they named MAF-wyu2 because it belongs to the metal-azolate frameworks (MAFs) [115]. The main characteristic of this new MOF is that it possesses rich open metal sites based on the planar trinuclear [Cu\({}_{3}\)(\(\mu_{3}\)-O)]\({}^{4+}\) clusters. This structure allows for higher catalytic activity to activate PMS, as well as remarkable thermal and chemical stability. Unlike other MOFs mentioned previously, the optimal conditions for this process are achieved when the initial pH is above 9, which allows for the complete removal of sulfamethoxazole in 60 min. Additionally, the stability of this MOF is very high, as its catalytic activity remains practically unchanged after five cycles.