Ordered mesoporous carbon CMK-3 was modified with cuprous chloride (CuCl) by a spontaneous thermal dispersion approach. A new kind of -complexation adsorbent was thus obtained and characterized by X-ray diffraction, N2 adsorption, and transmission electron microscopy. The results show that the mesostructure of CMK-3 is well preserved after the introduction of CuCl. In comparison with parent CMK-3, the selectivity of ethylene over ethane increases from 0.93 on CMK-3 to 2.67 on CuCl/CMK-3. All of the adsorption isotherms can be well fitted with the corresponding models. The fitting parameters along with the heat of adsorption demonstrate that the introduction of CuCl improve the interaction of ethylene with adsorbent apparently. The present adsorbents may provide useful candidates for the separation of ethylene and ethane as well as other alkene-containing systems.