Nitration and reduction route to surface groups of mesoporous carbons obtained from sucrose and phloroglucinol/formaldehyde precursors

Abstract

Mesoporous ordered carbons were obtained from two precursors, sucrose and phloroglucinol/formaldehyde, using a hard-template and a soft-template method, respectively. The surface of the materials was modified with the –NH2 groups via nitration and subsequent reduction of the resulting –NO2 groups. The modified carbon materials were investigated by elemental analysis, Boehm titration, nitrogen sorption, XRD, TEM, thermal analysis including TPD, as well as XPS and Raman spectroscopy. Apart from the –NO2 groups, the nitration step resulted in formation of the oxygen-rich surface species, the concentration of which decreased after reduction. This concerned especially the carboxylic groups, a part of which transformed into the amino acetate type of species. The sucrose-based method resulted in the materials with more abounding acidic groups then in the case of the phloroglucinol-based route. The number of the acidic groups decreased after the nitration in the following order: CMK-1 > CMK-3 >> CMK-8. On the contrary, the resistance of the carbon structures to the nitration/reduction processes conformed to the order of CMC-1 > CMK-3 >> CMK-1 ∼ CMK-8. The nitrogen content after the amination step exceeded slightly 2 wt.%. Such surface modifications provided attachment of the TCPP ligands, the amount of which ranged between ca. 30–60 wt.%.