This article presents a study on the synthesis and properties of ultrathin twisted carbon nitride nanoplates (PHI-NaCa) for efficient solar hydrogen production. The research focuses on improving light absorption and charge migration in poly(heptazine imide) (PHI) nanoplates. The study uses a binary molten salt of NaCl–CaCl₂ to synthesize PHI nanoplates with a distinctive nanoplate structure. The salt template allows the formation of thin nanoplates, promoting charge separation and migration. Additionally, the intercalation of Ca²⁺ ions between the conjugated layers activates the n–π* electron transition due to the distortion of in-plane heptazine layers. The optimized PHI nanoplates achieve an apparent quantum efficiency of up to 17.3% at 500 nm for photocatalytic hydrogen production. The study highlights the importance of rational control of optical absorption and charge carrier dynamics in poly(heptazine imide). The research also discusses the challenges of traditional carbon nitride materials, such as rapid carrier recombination and insufficient visible light absorption. The study proposes a new approach to overcome these limitations by using a binary molten salt system comprising CaCl₂. The results show that the twisted nanoplate structure enables the activation of the n–π* electron transition, extending visible light absorption up to 600 nm. The ultra-thin layer stacking reduces the distance of carrier migration, improving charge separation and migration. The study concludes that PHI-NaCa demonstrates exceptional photocatalytic H₂ production activity under visible light, with high stability and no evident activity decay after one month of storage. The research provides a new idea for the rational control of optical absorption and charge carrier dynamics in poly(heptazine imide).This article presents a study on the synthesis and properties of ultrathin twisted carbon nitride nanoplates (PHI-NaCa) for efficient solar hydrogen production. The research focuses on improving light absorption and charge migration in poly(heptazine imide) (PHI) nanoplates. The study uses a binary molten salt of NaCl–CaCl₂ to synthesize PHI nanoplates with a distinctive nanoplate structure. The salt template allows the formation of thin nanoplates, promoting charge separation and migration. Additionally, the intercalation of Ca²⁺ ions between the conjugated layers activates the n–π* electron transition due to the distortion of in-plane heptazine layers. The optimized PHI nanoplates achieve an apparent quantum efficiency of up to 17.3% at 500 nm for photocatalytic hydrogen production. The study highlights the importance of rational control of optical absorption and charge carrier dynamics in poly(heptazine imide). The research also discusses the challenges of traditional carbon nitride materials, such as rapid carrier recombination and insufficient visible light absorption. The study proposes a new approach to overcome these limitations by using a binary molten salt system comprising CaCl₂. The results show that the twisted nanoplate structure enables the activation of the n–π* electron transition, extending visible light absorption up to 600 nm. The ultra-thin layer stacking reduces the distance of carrier migration, improving charge separation and migration. The study concludes that PHI-NaCa demonstrates exceptional photocatalytic H₂ production activity under visible light, with high stability and no evident activity decay after one month of storage. The research provides a new idea for the rational control of optical absorption and charge carrier dynamics in poly(heptazine imide).