Methyl-terminated graphite carbon nitride with regulatable local charge redistribution for ultra-high photocatalytic hydrogen production and antibiotic degradation

Abstract

Intramolecular-tailored graphite carbon nitride (g-C₃N₄) has great potential to greatly optimize the photo-response performance and carrier separation ability, but exquisite molecular structure engineering is still challenging. Firstly, a series of oxygen and terminal methyl moiety co-modified g-C₃N₄ (CNNx) has been systematically prepared by using N-Hydroxysuccinimide (HOSu) as a novel copolymerized precursor and urea. The density functional theory (DFT) calculations demonstrated that the presence of oxygen can lower the binding energy for the C-C bond to make the terminal modification easier. The terminal methyl and Oxygen not only caused abundant alveolar defects to break the periodic symmetry but also acted as an electron-accepting platform to tune the local charge redistribution within g-C₃N₄ molecular. The synthesized CNNx (CNN25) achieved ultra-high photocatalytic activity and chemical stability under visible light toward antibiotic degradation (99% tetracycline, 92% doxycycline, 65% ofloxacin and 74% sulfathiazole degradation within 30 min) and hydrogen production (an apparent quantum efficiency of 2.10% at 400 nm). CNN25 also maintains good efficiency in surface water and groundwater. Moreover, the TC solution treated with CNN25 had hardly any harm to the growth of E. coli. We believe our findings will provide a facile and green strategy for the preparation of non-metallic modified g-C₃N₄.

Keywords: Antibiotic degradation; Defective engineering; Graphite carbon nitride; Nonmetallic modification; Photocatalysis.