Mesoporosity enhancement in carbon monoliths through incorporation of a nonpolar solvent with a templating source for fast adsorption of organic dyes

Abstract

Obtaining hierarchical porous carbon monoliths with bigger and controlled pore sizes through soft templating and without macroscopic phase separation remains a challenge for the synthesis. In this study, we tried to introduce nonpolar solvents (benzene or toluene) together with a pluronic template in the sol-gel polycondensation route of polymer precursors to obtain carbons in the monolithic form without macroscopic phase separation during the polymerization stage. The porosity results show that carbon monoliths vary solely with mesopore features while retaining macropores, compared to carbon monoliths obtained with pluronic template alone. The mesopore volumes almost double with an increase in pore sizes by 1 nm at maxima, and the pore sizes extend to 30 nm from the addition of nonpolar solvent. This is possible due to the interaction of the nonpolar solvent with the hydrophobic core of the pluronic template, which causes swelling of micelles during the polymerization stage, and thus finally, retention of larger pore sizes and pore volumes within carbon monoliths. The structural and surface chemistry characterizations ensure a similar behaviour of the resulting carbon monoliths that are further investigated for the adsorption kinetics of different types of organic dyes (methylene blue, methyl orange, and congo red) to understand the sole role of mesoporosity. The adsorption kinetics follows the trend of mesopore volumes with fast adsorption vis-à-vis the sizes and molar masses of organic dyes.