Covalent-organic framework derived nitrogen-enriched carbon: A remarkable adsorbent to remove 4-nitrophenol from water

Severe industrialization causes adverse impacts on human beings because of the contamination of water with toxic and undegradable organic contaminants such as phenolic compounds (PCs). Here, some nitrogen-rich carbonaceous materials, CDC(x)s, have been first prepared through the two-step carbonization of a covalent-organic framework SNW-1 (Schiff-based network-1). SNW-1 was pyrolyzed; the obtained product and potassium hydroxide mixtures were again pyrolyzed under different temperatures to get CDC(x)s. The carbonaceous materials were characterized and applied in the adsorptive elimination of para-nitrophenol (pNP, one of the representative PCs) from water. One CDC(x) called CDC(800) had a very high maximum adsorption capacity (Q_o), 1190 mg/g (at pH 7) which is 6 times that of activated carbon, and higher than that of any other known materials. Based on the adsorption results under various conditions, characteristics of CDC(800), and calculations, the plausible adsorption mechanism, such as hydrogen bonding (mainly between -NO₂ of pNP and H on the pyrrolic group of CDC(800)) and π-π interaction, could be suggested. Finally, the remarkable CDC(800) adsorbent was recyclable for several runs with ethanol washing; therefore, can be recommended as a competitive adsorbent to remove pNP from water.