Carbon Nitride Monolayers as a Promising Material for Toxic Formaldehyde Removal in Mitigation of Air Pollution

Overview

In recent decades, air pollution has been responsible for one of the greatest environmental health risks to humankind, responsible for up to 7 million premature deaths annually. Indoor air pollutants have garnered increasing attention due to human vulnerability to high levels of exposure. One such pollutant, formaldehyde (HCHO), is a toxic volatile organic compound (VOC), which accounts for more than 50% of cancer risks related to hazardous air pollutants, necessitating the development of materials for efficient removal. Two-dimensional (2D) monolayers have proven to be the best HCHO captor because of their exceptionally high surface-area ratio and tunable properties. In this study, first-principles calculations based on density functional theory (DFT) were employed to evaluate adsorption energy, charge transfer, and band gap, to optimize HCHO removal capabilities. We investigate formaldehyde adsorption by three 2D monolayers—C9N7, C7N3, and C2N—enhanced with phosphorus (P), germanium (Ge), and palladium (Pd) atom doping. Twenty-eight unique monolayer configurations were examined for doping, and the twelve most stable configurations were selected for adsorption assessment. Successful adsorption on five of these materials reveals that Ge-doped C9N7 has a strong adsorption energy of -2.354 eV followed by Pd-doped C7N3 at -1.603 eV. Both results reveal the untapped potential of C9N7 and C7N3, which surpass C2N (-1.244 eV), the current leader in HCHO adsorption. Furthermore, the adsorbed monolayer's band gaps have shown suitability for solar cell applications as an alternative to the wasteful disposal of used filters. These findings suggest that doped C9N7, C7N3, and C2N monolayers are promising candidates for capturing formaldehyde and subsequent utilization. Theoretical results are expected to stimulate experimental research for real material fabrication of two-dimensional monolayers for HCHO capture and the development of solar cell materials.

Competition history

• CSEF 2026 Environmental Engineering (Senior Division) · Entry S-11-08

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