## 4 Conclusions  
The ZnO/g-C3N4 composites synthesized in this study using a DES solvent demonstrated successful integration of ZnO and g-C3N4 structures, as confirmed by thorough structural and chemical characterizations. The material exhibited a porous nanosheet morphology with uniformly distributed elements, highlighting its suitability for catalytic applications. These results validate DES as an efficient and sustainable synthesis method to create advanced composites for environmental remediation.  
In terms of catalytic performance, the composites showed promising activity in various AOPs. Under irradiation at 395 nm, the photocatalytic degradation of Rhodamine B reached significant levels, demonstrating the ability of the material as a photocatalyst. This performance was further improved in the photo-Fenton-like process, where the synergistic activation of H2O2 and irradiation substantially improved the degradation rates. Optimization of the catalyst-to-H2O2 ratio was found to be a critical factor in maximizing the degradation efficiency. Nevertheless, the electro-Fenton-like process exhibited superior efficiency, achieving a rapid degradation of Rhodamine B with kinetic constants four times higher than anodic oxidation, highlighting the exceptional catalytic activity of ZnO/g-C\({}_{3}\)N\({}_{4}\). The reuse and stability studies revealed that the ZnO/g-C\({}_{3}\)N\({}_{4}\) composites maintained high degradation efficiencies during multiple cycles in both processes. The minimal decrease in catalytic activity and kinetic rate constants over successive cycles demonstrates the durability and long-term applicability of these composites in continuous or large-scale water treatment processes. This highlights the material's potential for operational flexibility in water treatment applications.  
The DES-synthesized ZnO/g-C\({}_{3}\)N\({}_{4}\) composites provide a sustainable and cost-effective solution for treating water contaminated with dyes. Their excellent catalytic performance, stability, and scalability make them a promising candidate for industrial wastewater treatment. Future research should focus on applying these composites to real-world wastewater conditions to further validate their industrial potential and explore their broader environmental impact.  
Conceptualization, B.L.-F. and M.A.S.; methodology, E.R. and M.A.S.; software, E.R.; validation, M.P., E.R. and M.A.S.; formal analysis, M.P. and E.R.; investigation, B.L.-F.; resources, M.P. and M.A.S.; data curation, E.R.; writing--original draft preparation, B.L.-F.; writing--review and editing, M.P., E.R. and M.A.S.; visualization, B.L.-F.; supervision, M.A.S.; project administration, M.A.S.; funding acquisition, M.A.S. All authors have read and agreed to the published version of the manuscript.  
This research has been supported by R&D Project PCI2022-132941 (BiodivRestore Cofund 2020) and TED2021-129590A-I00, funded by MICIU/ AEI/10.13039/501100011033, and by the European Union Next Generation EU/PRTR and R&D Project PID2020-113667 GB-I00, funded by MICIU/AEI/10.13039/501100011033.  
Not applicable.  
Data availability Statement: Data will be made available on request.  
The authors declare no conflicts of interest.