Recent progress in the applications of non-metal modified graphitic carbon nitride in photocatalysis

Over the past few decades, graphitic carbon nitride (g-C3N4) has gained increasing interest due to its unique and excellent properties. To improve its inherent drawbacks and perfect its catalytic performance, many convenient and facile strategies have been developed, including metal and non-metal modifications. However, the low content in nature and the leaching of toxic metals in photocorrosion have been two critical obstacles for metal-based photocatalysts in practical applications. Therefore, it is increasingly urgent to develop and design efficient and stable non-metal modified g-C3N4-based photocatalysts. Here, this review begins with a brief presentation of the unique characteristics of g-C3N4. Then, to maintain the metal-free nature of g-C3N4, the four most frequently used modification strategies are discussed, including vacancies introduction, doping with non-metal elements, modifying with non-metal quantum dots and coupling with other semiconductors. In addition, the latest developments of non-metal modified g-C3N4-based photocatalysts for energy-related and environmental applications are systematically discussed. In the end, both the current development bottlenecks and future development directions of g-C3N4-based metal-free photocatalysts are presented. Basically, we highlight the unique properties of completely non-metal modified g-C3N4, which has positive implications for the sustainable development of g-C3N4-based non-metal photocatalysts. Furthermore, we hope that it can spark new ideas and present promising directions to design metal-free photocatalysts for energy-related and environmental applications.