Controllable and rapid synthesis of nitrogen-doped ordered mesoporous carbon single crystals for CO2 capture

Abstract

The rapid synthesis of highly ordered nitrogen-doped mesoporous carbon single crystals with regular and tunable single-crystal morphologies were successfully realized via a controllable co-assembly strategy by using F127 as structure-directing template, 2-methylimidazole as nitrogen source and morphology-adjusting agent, and hexamethylenetetramine as formaldehyde source. Compared with other methods for carbon crystal growth, intricate pre-polymerization steps, taxing synthesis conditions, and long duration time are not requisite for this strategy. Detailed investigation on the effects of 2-methylimidazole dosage, hydrothermal temperature and time, and carbonization temperature on morphology, structure, and nitrogen content of carbon crystals were systematically conducted. Furthermore, one reasonable assembly mechanism was elucidated from both experimental and theoretical perspectives. It was found 2-methylimidazole actively involved in the formation of the polymer matrices via H-bonding to surfactant and chemical reactions with formaldehyde and resorcinol. As such, the introduced 2-methylimidazole not only acted as an effective nitrogen precursor to significantly promote the nitrogen content in resulted crystal carbons, but also served as a positive morphology-tuning agent. Its increasing use successfully achieved the morphology adjustment from hexagonal prisms to rhombic dodecahedrons and then spheres. With intrinsic enriched nitrogen content and large surface area, our synthesized carbon crystals show excellent CO2 adsorption performance.