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fluorescent feature, which makes it be served as bioimaging and fluorescence sensors. In addition, g-C 3 N 4 can be used as a drug carrier due to its π-π conjugation with the drug. It can thus be seen that g-C 3 N 4 is a 2D material with many functions in one. As a result, with the development of g-C 3 N 4 -based materials in biological fields, it is urgent to provide a comprehensive review of g-C 3 N 4 -based materials for biological applications.Like other applications, biological applications of g-C 3 N 4 -based materials are still limited by the reason of relatively large particles size, high recombination of carriers, and circumscribed visible-light absorption. [13] Therefore, in this review, the advanced synthesis approaches to improve the properties of g-C 3 N 4 -based materials are outlined and the different solutions to different problems of different applications are reported at great length. For example, three kinds of ways to improve the efficiency of photodynamic therapy (PDT) such as improving the near-infrared response of g-C 3 N 4 , [14] increasing oxygen levels in the microenvironment, [15] and reducing the glutathione (GSH) level in tumor cells are talked about. [16] Moreover, the biosafety and toxicity evaluations of g-C 3 N 4 -based materials are also conducted. Last, the challenges and personal opinions of g-C 3 N 4 -based materials in biomedical applications are discussed. It is hoped that this review could provide references and bases for further expanding the applications of g-C 3 N 4 in biomedical areas. Modification MethodsAt present, the photocatalytic performance of g-C 3 N 4 can be enhanced by defects, [17] hydrogen bond engineering, [18] and integrating with other semiconductors to form a heterojunction structure. [19] Defects EngineeringDefects engineering of g-C 3 N 4 includes vacancy defect and crystal defect. Vacancy in g-C 3 N 4 is served as effective capturing sites for photocarriers to promote charge separation and migration. [20] Doping is an impurity defect belonging to a crystal defect. Impurity defects generally do not change the crystal lattice of the original matrix, but will activate due to lattice malformation and provide conditions for the migration of particles.Metal-free graphitic carbon nitride (g-C 3 N 4 ) as a newly emerging nanomaterial has been employed in the biomedical field because of its special optical and electrical characterizations. This review summarizes diverse methods for preparing g-C 3 N 4 -based materials, and discusses contemporary advancements in biosensors, photocatalytic sterilization, photodynamic therapy, drug carrier, and biological imaging. The biosafety and toxicity evaluations of g-C 3 N 4 -based materials are discussed as well. The review ends with an overview and several insights on the challenges and opportunities of g-C 3 N 4 -based nanomaterials in this burgeoning field. This review is expected to provide inspiration for developing future g-C 3 N 4 -based materials for the biomedical applications.

Infectious diseases caused by bacteria intimidate the health of human beings all over the world. Although many avenues have been tried, various operating conditions limit their actual applications. Photocatalytic nanomaterials are becoming candidates to be competent for water purification. Here, a novel and more efficient S‐scheme has been engineered between two dimensional (2D) layered phosphorus‐doped graphitic carbon nitride (P‐g‐C3N4) and BiOBr via hydrothermal polymerization to inhibit the recombination of charge and broaden light absorption. The as‐prepared P‐g‐C3N4/BiOBr hybrids exhibits significantly improved photocatalytic disinfection contrast to g‐C3N4/BiOBr in visible wavelengths, suggesting phosphorus doping which adjusts the band structure plays a significant role in the S‐scheme system. And the sterilization rate of multidrug‐resistant Acinetobacter baumannii 28 (AB 28) was 99.9999% within 80 min and Staphylococcus aureus (S. aureus) was 99.9%.