Synthesis, structure and adsorption properties of nonstoichiometric carbon nitride in comparison with nitrogen-containing carbons

The samples of nonstoichiometric carbon nitride characterized by spatial ordering, large pore volume (up to 0.8 cm³/g) and specific surface area (up to 585 m²/g) were obtained via matrix carbonization of ethylenediamine in the presence of carbon tetrachloride in mesoporous molecular sieves KIT-6 and MCF as exotemplates. In contrast to nitrogen-containing carbons (obtained by modification of carbon samples with nitrogen in the result of compatible thermal treatment of the initial porous carbon with melamine) nonstoichiometric carbon nitride contains much more nitrogen (up to 13.7 wt.% (C/N = 6), compared with preceding 0.6 wt.%) and increased the quantity of basic nitrogen-containing groups (in particular, amino groups)—up to 0.68 mmol/g (vs. 0.46 mmol/g). The increase of adsorption capacity towards hydrogen and carbon dioxide: adsorption potential, differential heat of CO₂ adsorption, specific adsorption on the pore surface—from 5.4 to 7.3 μmol H₂/m² and from 2.2 to 5.4 μmol CO₂/m² for carbon and synthesized samples of nonstoichiometric carbon nitride, respectively, due to the incorporation of nitrogen atoms into the carbon framework was noticed.