Using metallic copper as reductant and tetrachloroethylene as carbon precursor, a simple, low temperature solvothermal method for the synthesis of horn shaped carbon nanotubes is reported. The detail study of reaction parameters such as temperature, time, carbon precursor amount, type and catalyst proportion has been carried out to optimize the conditions wherein that the copper metal (log) mediated reduction of tetrachloroethylene (25 mL) at 200 degrees C for 5 h resulted in the horn shaped carbon nanotubes with high yield and structural selectivity. The adsorption properties of horn shaped carbon nanotubes were investigated for carbon dioxide, methane, carbon monoxide and nitrogen as adsorbate by volumetric measurements up to 850 mm Hg. The prepared horn shaped carbon nanotubes showed good adsorption capacity for CO2 (45 cm(3)/g) and CO (17 cm(3)/g), at 303 K and 850 mmHg pressure, with high equilibrium selectivity (73.3 for CO2 and 110.7 for CO at 318 K) and capacity selectivity (9.1 for CO2 and 3.1 for CO at 850 mmHg and 318 K) over nitrogen which provides the tool for the separation of CO2 from its mixture with nitrogen observed in flue gas of thermal power plants and boilers, as well as with CO such as syngas. (C) 2012 Elsevier B.V. All rights reserved.