The graphitic phase carbon nitride (g-C₃N₄) is increasingly employed to remove heavy metals from wastewater, but the intrinsic imobilization mechanism still needs to be explored. Herein, the g-C₃N₄ before and after adsorption for Cu²⁺, Pb²⁺ and Zn²⁺ was firstly characterized using high resolution transmission electron microscope, energy dispersive X-ray, fourier transform infrared, and X-ray diffraction. Then two types of C₃N₄ structures were calculated, i.e. the triazine (C₃N₄a) and tri-s-triazine units (C₃N₄b) using the DFT theoretical calculation. The results indicated that the g-C₃N₄ materials possessed a well-developed 2D lamellar sturcture, basic tris-triazine units, and abundent C-N, C=N, –NH–, and –NH₂ groups. After scuccessfully adsorption for Cu²⁺, Pb²⁺ and Zn²⁺, the surface functional groups, typical tris-triazine units, and the amino functions of g-C₃N₄ were still well retained. The Cu²⁺, Pb²⁺ and Zn²⁺ ions combined with C₃N₄a and C₃N₄b, trapped in the hole surrounded by trazine molecules, and produced both three-cordinated [C₃N₄a-Cu/Pb/Zn]²⁺ and six-coordination [C₃N₄b-Cu/Pb/Zn]²⁺ structures. Interestingly, the heavy metals could be trapped within the C₃N₄b plane but be fixed above the C₃N₄a plane, and a higher sorpiton energy and coordination number were found for the structure of [C₃N₄b-Cu/Pb/Zn]²⁺ compared to [C₃N₄a-Cu/Pb/Zn]²⁺. In total, this study provides a new insight into the adsorption mechanism of g-C₃N₄ for heavy metal ions in water.

越来越多地采用石墨相氮化碳（gC ₃ N ₄）去除废水中的重金属，但内在固定化机理仍需探索。在此，首先利用高分辨率透射电子显微镜，能量色散X射线，傅立叶变换红外和X射线衍射表征了Cu 2 ⁺，Pb ²⁺和Zn ²⁺吸附前后的gC ₃ N ₄。然后计算出两种类型的C ₃ N ₄结构，即三嗪（C ₃ N ₄ a）和三-s-三嗪单元（C ₃ N ₄b）使用DFT理论计算。结果表明，gC ₃ N ₄材料具有发达的2D层状结构，基本的tris-triazine单元以及丰富的CN，C = N，-NH-和-NH ₂基团。在成功吸附Cu 2 ⁺，Pb ²⁺和Zn ^2+之后，仍保留了gC ₃ N ₄的表面官能团，典型的tris-triazine单元和氨基官能团。Cu 2 ⁺，Pb ²⁺和Zn ²⁺离子与C ₃ N ₄ a和C ₃ N _4结合b，陷于被三嗪分子包围的孔中，并产生了三配位的[C ₃ N ₄ a-Cu / Pb / Zn] ²⁺和六配位的[C ₃ N ₄ b-Cu / Pb / Zn] ^{2 +}结构。有趣的是，重金属可能被捕集在C ₃ N ₄ b平面内，但被固定在C ₃ N ₄ a平面上方，并且发现[C ₃ N ₄ b-Cu]结构具有更高的索顿能和配位数。/ Pb / Zn] ²⁺与[C ₃ N ₄ a-Cu / Pb / Zn] ²⁺。总的来说，这项研究为gC ₃ N ₄对水中重金属离子的吸附机理提供了新的见解。