Separation of alkane isomers in a hierarchically structured 3D-printed porous carbon monolith

•3D-printed carbon-based monoliths were studied in adsorptive alkane isomer separation.•Fixed bed breakthrough experiments were conducted for C5/C6 isomer feed mixtures.•The pristine monolith shows a near molecular sieving effect for the branched alkanes.•The CO2-activated monoliths significantly adsorbed all the alkane isomers.•A dynamic fixed bed adsorption model is developed to simulate the experimental data.