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The synergistic effect of sodium and oxygen expands π-conjugated aromatic rings and distortion of the heptazine skeleton, enhancing the intrinsic π→π* electron transition and the effective n→π* electron transition. [Display omitted] • A sodium and oxygen co-doped g-C 3 N 4 (NaOCN) is prepared by facile microwave synthesis, in which Na as a charge transport channel promotes the separation efficiency of photogenerated carriers. • The as-prepared NaOCN exhibits the NIR absorption extended to 1400 nm and the apparent quantum yield (AQY) can keep 26.9% at 420 nm and still maintain 7.2 % at 600 nm, which shows strong NIR response range. • The intrinsic π → π* electron transition and active the n → π* electron transition generated by the synergistic effect of Na and O atoms are the main factor to promote the NIR response of NaOCN. Efficient utilization of near-infrared light (NIR) is critical to optimize the performance of photocatalysts. Herein, an ultrafast process is employed to co-condensation of melamine and NaCl by microwave-assist heating. The fabricated sodium and oxygen co-doped g-C 3 N 4 (NaOCN) shows extended π-conjugated aromatic rings and distortion of the heptazine skeleton, which can enhance the intrinsic π → π* electron transition and active the n → π* electron transition. The robust n → π* excitation of NaOCN leads to a narrowed bandgap of 2.73 eV with the NIR absorption extending to 1400 nm. The apparent quantum yield (AQY) for NaOCN can still keep 7.2 % at 600 nm. This work provides a promising way for the application of NIR-based carbon nitride in photocatalytic H 2 O 2 production. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C 3 N 4) faces limitations in photocatalytic application due to its limited light response and high recombination rate of photo-generated charge carriers. Herein, we synthesized a K, P co-doped g-C 3 N 4 (KPCN) with cyano defects via microwave-assisted heating of the mixture of KH 2 PO 4 and melamine in just 7 min. The KPCN exhibits a reduced bandgap of 2.37 eV and introduces a mid-gap of 1.77 eV, which broadens light absorption to the visible-near-infrared (vis-NIR) spectrum with light absorption to 867 nm. Impressively, the co-doped K and P adjust the interlayer and in-plane electron distribution of g-C 3 N 4 , enhancing charge separation and transfer. The KPCN exhibits a remarkable improvement in H 2 O 2 yield of 7.74 mM g−1 h−1, demonstrating superior catalytic activity compared to microwave pure g-C 3 N 4 (MCN, 5.1 times) and bulk g-C 3 N 4 (BCN, 19.2 times). The results indicate that the K, P co-doped g-C 3 N 4 synthesized rapidly and efficiently by microwave method has relatively stable and considerable photocatalytic activity, which has great potential application in the industrial production of H 2 O 2. • K, P co-doped g-C 3 N 4 (KPCN) was prepared by rapid microwave synthesis in just 7 min. • K, P co-doping optimizes the in-plane electron distribution and interlayer electron migration of g-C 3 N 4. • KPCN exhibits a reduced bandgap from 2.75 eV to 2.37 eV and introduces a mid-gap at 1.77 eV. [ABSTRACT FROM AUTHOR]