Environmental remediation by microporous carbon: An efficient contender for CO₂ and methylene blue adsorption

Nitrogen-doped microporous carbons with extremely narrow pore size distribution were derived from sucrose and melamine with the molten LiCl/KCl salts acting as a template to generate pores. A high CO₂ uptake of up to 197 mg/g at 273 K and 1 bar was observed, revealing the significance of the pore size (0.84 nm) for CO₂ capture. Our findings demonstrate that the nitrogen-doped SMLK-1 has a large surface area (951 m²/g) and large micropore volume (0.42 cm³/g) with high nitrogen-content (11.2 at.%), but the adsorption capacity (180 mg/g at 273 K, 1 bar) is comparable to that of un-doped SMLK-0 (S_BET = 520 m²/g, V_micro = 0.26 cm³/g). The CO₂ uptake capacity per pore volume and volume fraction of the pores (<0.84 nm) in total pore volume exhibit a straight-line graph with a high correlation coefficient of 0.93 revealing that the adsorption capacity of the carbonaceous adsorbents may strongly rely upon the fine pore size distributions. Moreover, the prepared materials were also investigated as adsorbents for methylene blue from an aqueous solution. The sample with a melamine-to-sucrose ratio of 0 (SMLK-0) exhibited the excellent dye adsorption, 134.7 mg/g for an initial methylene blue concentration of 25 × 10^-2 mM and 31.1 mg/g for an initial concentration of 5 × 10^-2 mM. Therefore, the fabrication method presented here permits the fine-tuning of the pore network to exploit the prepared materials both as CO₂ and dye adsorbents for environmental remediation.