Three-dimensional (3D) carbon nitride (C₃N₄) can be used as a metal-free platform for visible-light-active photocatalysts because of its suitable band positions. This study reports that HNO₃ activation improves the photocatalytic activity of 3D melamine-derived C₃N₄ (MCN) materials, which degrade the organic pollutant rhodamine B (RhB). HNO₃ treatment under reflux removes the carbonaceous impurities in MCN and introduces oxygen-containing functional groups on its surface. Under visible light irradiation, the nitric acid treated MCN (NT-MCN) completely degrades RhB within 30 min. Photophysical characterizations and control experiments with radical scavengers reveal that MCN and NT-MCN follow different reaction mechanisms. Because NT-MCN exhibits a longer photoluminescence lifetime, smaller electrochemical resistance, and larger photocurrent than those of MCN, it enables a more efficient and facile transfer of photogenerated charge carriers for the degradation reaction.

三维（3D）氮化碳（C ₃ N ₄）由于其合适的能带位置，可以用作可见光活性光催化剂的无金属平台。这项研究报告说，HNO ₃活化可改善3D三聚氰胺衍生的C ₃ N ₄（MCN）材料的光催化活性，从而降解有机污染物若丹明B（RhB）。HNO ₃回流下的处理除去了MCN中的碳质杂质，并在其表面引入了含氧官能团。在可见光照射下，硝酸处理的MCN（NT-MCN）在30分钟内完全降解RhB。自由基清除剂的光物理特征和控制实验表明，MCN和NT-MCN遵循不同的反应机理。由于NT-MCN与MCN相比，具有更长的光致发光寿命，更小的电化学电阻和更大的光电流，因此它能够更有效，更轻松地转移光生电荷载流子，以进行降解反应。