## 1 Introduction  
The widespread use of antibiotics, particularly tetracycline hydrochloride (TCH), in agriculture, aquaculture, and healthcare has led to its persistent presence in aquatic ecosystems. Due to its low biodegradability and the potential to induce antibiotic resistance, TCH poses a significant environmental risk. Studies have reported TCH concentrations in wastewater as high as 1708.33 ng/L [1], threatening aquatic organisms by disrupting microbial communities and food chains. Furthermore, the persistence of TCH in water systems facilitates the development of antibiotic-resistant bacteria, which can be transferred through the water cycle, ultimately posing health risks to humans [2, 3]. Given its persistence and widespread occurrence, there is an urgent need for effective strategies to remove TCH from contaminated water sources. A range of traditional techniques, such as biological degradation, adsorption, and advanced oxidation processes, are commonly utilized in the treatment of wastewater [4]. However, these approaches show limited efficiency in dealing with persistent organic pollutants such as TCH. Photocatalysis, as an emerging technology, offers a promising alternative by utilizing light to degrade pollutants [5]. Nevertheless, widely studied photocatalysts such as TiO\({}_{2}\) and ZnO exhibit limited visible light responsiveness and experience fast recombination of photo-induced carriers, significantly limiting their practical application in wastewater treatment. To address these challenges, materials based on g-C\({}_{3}\)N\({}_{4}\) have been extensively explored for their excellent chemical stability, visible light absorption, and cost-effective synthesis. When combined with semiconductors such as TiO\({}_{2}\)[6], ZnO [7], and Bi\({}_{2}\)WO\({}_{6}\)[8], g-C\({}_{3}\)N\({}_{4}\) demonstrates enhanced photocatalytic efficiency. Unfortunately, challenges such as rapid electron-hole recombination and insufficient surface areas for pollutant adsorption persist [9; 10]. Recent advancements, such as surface area enhancement, pore morphology modulation, and semiconductor coupling [11; 12], have achieved some success in improving g-C\({}_{3}\)N\({}_{4}\)'s performance. For instance, [PERSON] et al. [13] developed Ni\({}_{2}\)P/g-C\({}_{3}\)N\({}_{4}\) via hydrothermal methods, achieving enhanced hydrogen evolution and sterilization when exposed to light in the visible spectrum. Similarly, [PERSON] et al. [14] prepared Sm-doped g-C\({}_{3}\)N\({}_{4}\)/Ti\({}_{3}\)C\({}_{2}\) MXene, achieving a degradation efficiency exceeding 99% for ciprofloxacin. Additionally, [PERSON] et al. [15] developed a direct Z-scheme \(\alpha\)-Bi\({}_{2}\)O\({}_{3}\)/g-C\({}_{3}\)N\({}_{4}\) composite photocatalyst via thermal treatment, demonstrating efficient degradation of organic dyes with good stability and reusability. While doped and hybridized g-C\({}_{3}\)N\({}_{4}\) composites have shown notable progress, critical challenges remain in further optimizing the absorption of light in the visible range and ensuring efficient charge carrier separation. To bridge this gap, integrating complementary materials has proven to be an effective strategy. g-C\({}_{3}\)N\({}_{4}\)/TiO\({}_{2}\) systems are limited by TiO\({}_{2}\)'s narrow UV absorption, while g-C\({}_{3}\)N\({}_{4}\)/ZnO composites suffer from high recombination rates [16], reducing photocatalytic efficiency. This study proposes a novel CdS/porous g-C\({}_{3}\)N\({}_{4}\) heterostructure, combining the complementary properties of CdS and g-C\({}_{3}\)N\({}_{4}\) to enhance photocatalytic performance under visible light [17]. By contrast, The narrow bandgap of CdS (2.1-2.4 eV) [18] broadens visible light absorption [19], enabling more efficient utilization of solar energy [20]. Simultaneously, the porous architecture of g-C\({}_{3}\)N\({}_{4}\) enhances the specific surface area, creating more reaction centers [21] and providing a high density of adsorption sites for TCH [22], thereby accelerating the degradation process [23].