###### Abstract  
Carbon quantum dots (CDs) are a fascinating class of carbon nanomaterials (less than 10 nm in size) with unique optical, electrical, and physicochemical properties. In addition to these properties, CQDs exhibit the desired advantages of aqueous stability, low toxicity, high surface area, economic feasibility, chemical inertness, and highly tunable photoluminescence behaviour. Recently, graphitic carbon nitride (g-C\({}_{3}\)N\({}_{4}\)) has appeared as one of the required stable carbon-based polymers due to its varied applications in several fields. In this regard, modification strategies have been made in the g-C\({}_{3}\)N\({}_{4}\) semiconductor using CQDs to enhance the adsorptive and photocatalytic activity. In comparison to other semiconductor quantum dots, g-C\({}_{3}\)N\({}_{4}\) shows strong fluorescent properties, such as wide excitation spectra, photostability, and tunable photo-luminescent emission spectra. The interaction inside this multicomponent photocatalyst further promotes the photocatalytic activity by improving charge transference, which plays a vital role in electrochemistry. Therefore, CQDs are suspicious nanomaterials in the field of photocatalysis, wastewater treatment and water adsorption treatment. This particular article featured the recent progression in the field of CDs/g-C\({}_{3}\)N\({}_{4}\)-based photocatalysts focusing on their luminescent mechanism and potential applications in wastewater treatment. g-C\({}_{3}\)N\({}_{4}\); carbon quantum dots; nanocomposite; pollutant degradation; CO\({}_{2}\) reduction +
Footnote †: journal: Applied  
of researchers on TiO\({}_{2}\) photocatalysis [15; 16; 17]. Thereafter, a number of semiconductors photocatalysts, involving TiO\({}_{2}\)[18], SrTiO\({}_{3}\)[19; 20], black phosphorus [21], ZnO [20; 22; 23], and Bi\({}_{2}\)MO\({}_{6}\)[24], have been fabricated and broadly studied with the application in organic pollutants photodegradation [25; 26], H\({}_{2}\) evolution [27], and CO\({}_{2}\) reduction into solar fuels [28; 29]. Additionally, [PERSON] et al. summarized the research related to the solar light-assisted photodegradation of persistent water pollutants through the generation of \({}^{\bullet}\)OH free radicals [30]. However, a potential semiconductor photocatalyst should have characteristic features, including suitable band-edges positions, appropriate band energy, high surface area, and more electron-hole pair separation and mobility as delineated in (Figure 1) [31]. These desirable features, such as high surface area due to the formation of nanoparticles, leading to high adsorption, efficient charge separation due to preferential migration along a certain direction, and suitable band-positioning, fulfilling the requirement of \({}^{\bullet}\)OH, \({}^{\bullet}\)O\({}_{2}\)\({}^{-}\) free radicals [32; 33]. In recent years, many unprecedented pieces of research were found in the field of environmental and wastewater treatments through advanced oxidation technologies (AOTs), as one category of chemical methods, which have been indicated as one of the most alluring and effectual solutions for the degradation of organic pollutants [34; 35]. The merits of these processes relative to other conventional methods are due to (i) complete degradation of the persistent complexes and their intermediate products without generation of any secondary by-products, (ii) cost-effectiveness, and (iii) optimum temperature and pressure conditions being easily determined [9; 36]. In particular, these processes generated highly reactive oxygen species (ROS), such as \({}^{\bullet}\)OH, \({}^{\bullet}\)O\({}_{2}\)\({}^{-}\), \({}^{1}\)O\({}_{2}\), \({}^{\bullet}\)SO\({}_{4}\)\({}^{-}\), and h\({}^{+}\), when reacted with H\({}_{2}\)O/\({}^{-}\)OH or dissolved oxygen, facilitating the degradation of nonibodegradable organic compounds into simpler molecules (H\({}_{2}\)O and CO\({}_{2}\)) [37]. The strong oxidizing capability of ROS and  
Figure 1: The main features of a potential photocatalyst. Adapted from Ref. [31].