Salt-templated synthesis of 3D porous foam-like C3N4 towards high-performance photodegradation of tetracyclines

Abstract

Photocatalysis has emerged as an efficient method to treat highly noxious and persistent antibiotics such as tetracyclines (TCs) in the ecological environment. Carbon nitride (C₃N₄) is one promising photocatalyst, but the synthesis of C₃N₄ with a tunable chemical structure, extended visible-light harvesting, and strong photoactivity remains a challenge. Herein, 3D porous foam-like C₃N₄ (F-C₃N₄) was facilely prepared by thermal polycondensation of melamine with salt templates. F-C₃N₄ bears a hierarchically porous structure with a moderate specific surface area of 50.3 m² g⁻¹, which is 12 times higher than that of bulk C₃N₄. Besides, F-C₃N₄ shows a shorter average lifetime of photoexcited charge carriers and a stronger photocurrent response than bulk C₃N₄, since the hierarchical pores and functional groups of F-C₃N₄ promote the migration of photoinduced charge carriers. The high photocatalytic activity of F-C₃N₄ is displayed in the degradation of TC, for which the kinetic constant is 64 times higher than that of bulk C₃N₄. Finally, the photodegradation mechanism of TC is revealed by detecting reactive oxygen species such as OH˙, ¹O₂ and O₂˙⁻ through electron paramagnetic resonance, as well as analyzing the intermediate degradation products of TC. This work provides a facile method to prepare porous C₃N₄ with a remarkably enhanced photocatalytic activity.