Equilibrium adsorption studies of CO2, CH4 and N-2 were carried out with polystyrene based adsorbent, functionalized with heterocyclic ligands, viz. citrazinic acid (CA), 4-hydroxymethyl pyridine (MP) and 2,6-bis-imidazo-1-yl-pyridine-4-carboxylic acid (BIMP) using batch adsorption and pulse chromatography technique. The equilibrium uptakes of CO2, CH4 and N-2 for all the adsorbents were determined at atmospheric and high pressures. The equilibrium adsorption constants and selectivities were estimated by fitting of experimental chromatograms obtained from pulse chromatography studies into linear equilibrium dispersive chromatography model using gPROMS. The BIMP functionalized polystyrene adsorbent showed the highest equilibrium uptake and selectivity for CO2. (C) 2016 Published by Elsevier B.V.