Ferromagnetism manipulation on 2D carbon nitrides by substituents with different electronic effects

With weak spin-orbital coupling and a unique band structure, graphitic carbon nitride (g-C 3 N 4 ) is an ideal candidate for a 2D metal-free ferromagnetic material that can be used in next-generation spintronics. Despite the achievements in room-temperature ferromagnetic g-C3N4, rational optimization of its ferromagnetism still remains challenging. Theoretically, ferromagnetism of 2D materials can be optimized by engineering their band structure, analogous to the concept of HOMO-LUMO in chemistry. Considering the HOMO-LUMO structure is prone to be modulated by substituents with different electronic effects, this work attempts to modulate the band structure of g-C3N4 by introducing different substituents through a simple and efficient strategy. With band structure optimization, the ferromagnetism of g-C 3 N 4 is significantly enhanced by electron-withdrawing nitrobenzene groups, as compared to electron-donating aminobenzene. The enhancement of ferromagnetism is ascribed to the reduction of the bandgap and conduction band energy, as evidenced by experimental and theoretical analyses. By introducing substituent with different electronic effect, band structure of graphitic carbon nitride (g-C 3 N 4 ) is effectively modulated. Specifically, electron-withdrawing substituent (nitrobenzene) simultaneously reduced the bandgap and conduction band of graphitic carbon nitride, which facilitate the electronic population at the “majority spin” state. As results, significant ferromagnetic enhancement and elevated Curie temperature were achieved. • Substituents with different electronic structures were introduced into 2D g-C 3 N 4 • Band structure of g-C 3 N 4 were modulated upon introduction of substituents. • Electronic population of g-C 3 N 4 were tuned by band structure modulation. • Magnetism of g-C 3 N 4 is enhanced by electron-withdrawing (nitrobenzene) substituent.