Mechanism of Formaldehyde Removal by Graphitic Carbon Nitride (g-C₃N₄): g-C₃N₄ efficiently removes formaldehyde under ambient visible light(e.g., fluorescent or LED lamps) via metal-free photocatalytic oxidation: When photons with energy ≥ g-C₃N₄’s bandgap (~2.7 eV) strike the catalyst, electrons are excited from the valence band to the conduction band, generating highly reactive photogenerated electrons (e⁻) and holes (h⁺). - The holes (h⁺) oxidize adsorbed H₂O to produce powerful hydroxyl radicals (·OH); - The electrons (e⁻) reduce O₂ to generate superoxide radicals (·O₂⁻); - These radicals synergistically oxidize formaldehyde (HCHO) stepwise—first to formic acid (HCOOH) and hydrogen peroxide (H₂O₂), and ultimately mineralize it completely into harmless CO₂ and H₂O . This process does not consume the catalyst, enabling long-term stability. Moreover, g-C₃N₄’s advantages—including metal-free composition, excellent thermal/chemical stability, and strong visible-light response—make it far more suitable for indoor use than conventional TiO₂ (which requires UV light and exhibits only ~4% solar utilization)