Engineering Triune\nActive Sites on Alkali Metal-Doped\nGraphite Carbon Nitride for Aqueous Catalytic Ozonation

Novel alkali metal-doped graphite carbon nitride (CN)\ncatalysts\n(CN–M, where M = K, Na, or Li) with triune active sites (alkali\nmetal atoms, cyano groups, and N vacancies) prepared by one-step pyrolysis\nto enhance the catalytic ozonation performance of pristine CN. The\nstructural analysis of CN–M and the significant enhancement\nadsorption of ozone performance are demonstrated by density functional\ntheory calculations and experiment tests. The insertion of alkali\natoms can shorten the distance between the layers, forming an electronic\nbridge and accelerating the transfer of electrons. Cyano groups serve\nas strong electron-withdrawing groups that effectively modulate the\nelectronic structure of the CN surface. N vacancies ulteriorly optimize\nthe charge distribution on the surface of the material and promote\nozone adsorption. The prepared CN–Na, CN–K, and CN–Li\ncatalysts exhibit excellent atrazine (ATZ) degradation efficiencies\nof 99.6%, 97.0%, and 94.0%, respectively, that greatly exceed that\nof CN (62.8%) and single ozone oxidation (54.8%). The toxicity results\nof the ATZ intermediates show a significant toxicity reduction in\nATZ after the heterogeneous catalytic ozonation process. This study\nprovides insights into the synergistic interactions of alkali metal\natoms, cyano groups, and N vacancies, which will help to guide and\ndesign triune active site CN-based catalysts for enhanced ozone activation.