Development of visible light active crystalline carbon nitrides for photocatalytic degradation of microplastics

Plastic-based products are widely used in almost all aspects of our daily lives owing to their durability, low cost, and portability. However, these tiny pieces of plastic, known as microplastics, that enter our waterways have been acknowledged as a major contributor to water pollution, especially in seawater. In addition, these products are significantly impacting both human health and the environment on a global scale. Therefore, the full removal and degradation of microplastics from seawater is an important challenge in the 21st century. In removing organic-based compounds, the photocatalytic oxidation process using titanium dioxide (TiO2) has been acknowledged as one of the promising methods. However, since sunlight comprises 45% of the visible light spectrum and TiO2 only works excellently under ultraviolet (UV) light, a new visible light active material is required. Recently, crystalline carbon nitride (CN) has attracted worldwide attention, particularly in the field of photocatalysis, due to its low cost, environmental friendliness, and tunable structures. Unfortunately, some limitations associated with CN materials are their relatively low surface area and high band gap energy, which subsequently affect their photocatalytic performance. Therefore, constructing crystalline CN with a larger surface area that is highly active under visible light can be a challenging task. In this study, a mesoporous crystalline CN will be prepared to improve its surface area, while a dopant with a chemical structure similar to CN will be incorporated within the CN triazine structure to improve its visible light response. Their large surface area would facilitate the accumulation of more microplastics into the CN structure for the photocatalytic process to occur, while the addition of a dopant would enhance CN's light absorption in longer wavelengths.