g-C₃N₄ has recently emerged as a promising photocatalyst for solar energy conversion. Nonetheless, attempts to enhance its inherently low activity are rarely based on precise molecular tunability strategy. In this study, two-type cyanamide defects-grafting g-C₃N₄ (CCN) was prepared through the thermal polymerization of thiourea in the presence of KCl. Stable potassium isothiocyanate (KSCN) was in situ generated via thiourea isomerization and then reacted with different amino groups (NH₂ and NH) in tri-s-triazine rings to obtain two-type cyanamide defects. Theoretical calculations and experiment results confirm that the ratio of the two-type cyanamide defects could be adjusted by KCl dosage, accompanying tunable energy levels of CCN. The charge carrier transfer and separation of CCN was greatly improved. Furthermore, the existence of cyanamide defects hindered the formation of intermolecular hydrogen bonds among g-C₃N₄, which facilitated the formation of porous structure and exposed more active sites for photocatalytic hydrogen evolution reaction (HER). As a result, the optimized photocatalyst (CCN-0.03) showed a high HER rate of 4.0 mmol g⁻¹h⁻¹, which was 5 times higher than 0.8 mmol g⁻¹h⁻¹ for pristine g-C₃N₄. And the apparent quantum efficiency reached up to 14.65% at 420 ± 10 nm. The findings deepen the understanding on precise molecular tuning of g-C₃N₄.

最近，gC ₃ N ₄成为一种有前途的用于太阳能转化的光催化剂。但是，很少尝试基于精确的分子可调性策略来增强其固有的低活性。在这项研究中，通过在KCl的存在下硫脲的热聚合反应制备了两种类型的氨基氰缺陷接枝物gC ₃ N ₄（CCN）。通过硫脲异构化原位生成稳定的异硫氰酸钾（KSCN），然后与不同的氨基（NH ₂和NH）在三-s-三嗪环中获得两种类型的氰胺缺陷。理论计算和实验结果证实，可以伴随着CCN的可调节能级，通过KCl剂量来调节两种氰胺缺陷的比例。CCN的载流子转移和分离得到了极大的改善。此外，氰胺缺陷的存在阻碍了gC ₃ N ₄之间分子间氢键的形成，这促进了多孔结构的形成，并暴露了更多的光催化氢释放反应（HER）活性位。结果，优化的光催化剂（CCN-0.03）显示出4.0 mmol g ^-1 h ^-1的高HER率，是0.8 mmol g ^-1 h的5倍。^-1对于原始gC ₃ N ₄。在420±10 nm处，表观量子效率高达14.65％。这些发现加深了对gC ₃ N ₄精确分子调谐的理解。