Solvent-free mechanochemical synthesis of N-doped mesoporous carbons for CO2 capture

Abstract

The increasing concentration of CO₂ in the atmosphere is a critical environmental issue, directly contributing to global warming and natural disasters. While clean energy alternatives are essential, the immediate capture of CO₂ is necessary to mitigate short-term environmental impacts. Among various CO₂ capture technologies, adsorption processes using porous materials have shown significant promise. However, materials generally used in recent studies, due to their high adsorptive capacity, such as zeolites and metal–organic frameworks (MOFs), have high costs. In this context, mesoporous carbons (MCs) have emerged as a promising and affordable alternative due to their stability, high surface area, and wide pore sizes. The incorporation of nitrogen into the carbon matrix further enhances CO₂ adsorption by increasing the material's basicity, improving CO₂ affinity, and creating additional active sites for adsorption. This work explores the synthesis of nitrogen-doped mesoporous carbons using a sustainable, solvent-free mechanochemical method. By varying the ratio of the carbon precursor (resorcinol) to the nitrogen precursor (melamine), the textural properties of the resulting materials can be tailored, leading to the formation of macro- and micropores and disordered porous structures. The MCN14 (9.05% of nitrogen in the carbon matrix) material exhibited the best textural parameters. In CO₂ adsorption studies, the pure MC material demonstrated adsorption capacities of 1.9 mmol g⁻¹ and 4.3 mmol g⁻¹ at 1.0 and 9.5 bar, respectively, while the nitrogen-doped MCN14 reached 2.3 mmol g⁻¹ and 3.9 mmol g⁻¹. These results indicate that both pore volume and nitrogen doping sites play a key role in enhancing CO₂ adsorption capacity at low pressures. This study highlights the effectiveness of the solvent-free method in producing high-performance, sustainable, and scalable nitrogen-doped carbon materials for CO₂ capture.