The objective of the present work is to develop a simple procedure, which avoids the need of a binder, to obtain activated carbon monoliths from a waste precursor (coal tar pitch) suitable for CO2 capture and/or separation. The main task of this process consists of a nitration process of the coal tar pitch. This nitration step over the coal tar pitch is characterised by different techniques, such as infrared spectroscopy and thermogravimetric analysis. The nitration treatment produces the oxidation of the pitch molecules, leading to hydrogen consumption and generating oxygenated and nitrogenated surface complexes. As a consequence of this oxidation, nitrated coal tar pitch is an infusible material, which allows the carbonization of monolithic pieces avoiding their fusion. Decomposition of these surface complexes during the carbonization of monoliths generates narrow microporosity, which is suitable for CO2 capture from gas streams at room temperature. The molecular sieving properties of these materials are studied by CH4 and CO2 adsorption kinetics. (c) 2010 Elsevier B.V. All rights reserved.