Facile synthesis of highly crystalline g-C3N4 nanosheets with remarkable visible light photocatalytic activity for antibiotics removal.

g-C3N4 has attracted much attention in photocatalysis field because of its good visible light response. However, its photocatalytic activity is still greatly limited by fast carriers recombination and small specific surface. In order to promote carriers separation and pollutants adsorption, a facile synthesis scheme combining hydrothermal method with secondary calcination process under N2 gas protection was developed, and highly crystalline g-C3N4 nanosheets (HCCNNS) were successfully prepared. During ciprofloxacin (CIP) and sulfamethazine (SMZ) degradation, it showed excellent visible light photocatalytic activity, wherein CIP and SMZ with 10 mg/L could achieve degradation efficiency of 98.4% and 96.9% in 60 min under visible light irradiation. Compared with conventional g-C3N4, the degradation rate constants were enhanced by 6.9 and 5.8 times, respectively. From the perspectives of morphology, optical property and surface chemistry, the ultra-high activity of HCCNNS is mainly attributed to its highly crystalline structure and nanosheet morphology, which not only reduce the carriers transfer resistance, promote the pollutants adsorption capability, but also expand the light absorption range, and promote the carriers separation. Furthermore, the synthesis procedure of HCCNNS possesses the nature of high yield and excellent cost performance, thus, HCCNNS possesses great potential for mass production and practical application for antibiotics removal.