Graphitic carbon nitride (C₃N₄) is a promising photocatalyst due to its suitable band gap and polymer properties, but its efficiency is limited by the poor separation of photoinduced electron/hole (e^–/h⁺) pairs. To address this issue, we propose creating N vacancies within the layers and bridging K single-atoms between the C₃N₄ layers through the self-assembly of potassium citrate and melamine–urea monomers. The introduction of N vacancies disrupts the symmetry of C₃N₄, promoting electron transfer along the delocalized π-conjugated network, while the presence of K atoms provides channels for electron transfer between the layers by forming N–K–N bridges, thereby leading to significant enhancement in the separation and transfer of e^–/h⁺ pairs across spatial dimension. As expected, the co-modified C₃N₄, with N vacancies and K single-atoms (designated as CN-K-V_N), exhibits excellent photocatalytic performance, with reaction rate constant of 9.69×10^–2 min^–1 (7.39×10^–2 min^–1 in real water environment) for tetracycline, achieving 80% degradation of tetracycline within 20 minutes. The reaction mechanism, as well as the toxicity of the degradation intermediates, is deeply discussed. This study provides a strategy to enhance the spatial separation of electrons for photocatalyst, highlighting its significance role in photocatalysis.

中文翻译：

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C3N4 中 N 空位和 K 单原子的双位工程：为光催化实现空间电荷转移通道


石墨氮化碳 （C₃N₄） 由于其合适的带隙和聚合物特性而是一种很有前途的光催化剂，但其效率受到光诱导电子/空穴 （e^–/h⁺） 对分离不良的限制。为了解决这个问题，我们建议在层内创建 N 空位，并通过柠檬酸钾和三聚氰胺-尿素单体的自组装在 C₃N₄ 层之间桥接 K 单原子。N 空位的引入破坏了 C₃N₄ 的对称性，促进了沿离域 π 共轭网络的电子转移，而 K 原子的存在通过形成 N-K-N 桥为层间的电子转移提供了通道，从而导致 e^-/h⁺ 对在空间维度上的分离和转移的显着增强。正如预期的那样，共修饰的 C₃N₄ 具有 N 空位和 K 单原子（指定为 CN-K-V_N），表现出优异的光催化性能，对四环素的反应速率常数为 9.69×10^–2 min^–1（在实际水环境中为 7.39×^10–2 min^–1），在 20 分钟内实现 80% 的四环素降解。深入讨论了反应机理以及降解中间体的毒性。本研究提供了一种增强光催化剂电子空间分离的策略，突出了其在光催化中的重要作用。