Mesoporous carbon nitrides with well-ordered 3D porous structure and large, tuneable cage-type mesopores (MCN-7) have been prepared through a straightforward polymerization of ethylenediamine (EDA) and carbon tetrachloride (CTC) inside the pore channels of FDU-12 with different pore diameters. The obtained MCN-7 were characterized using small angle X-ray diffraction, N-2 adsorption, high resolution transmission electron microscopy (HRTEM), high resolution scanning electron microscopy (FE SEM), Fourier transform infra-red, electron energy loss and X-ray photoelectron spectroscopy, and CHN analysis. The characterization results reveal that the structure of the MCN-7 is highly ordered and the pore structure of the templates are perfectly replicated into the carbon nitrides (CN). Nitrogen adsorption results indicate that the pore diameter of MCN-7 is directly controlled by the pore diameter of the template and can be tuned with a simple adjustment of the pore size of the template. The XPS and FT-IR data confirm that the wall structure of the samples are composed of CN framework with terminal amine groups that are exposed on the surface and are important for the capture of CO2 molecules. MCN-7 with different pore diameters and specific surface area are used as adsorbents for the capture of CO2 molecules at different high pressures (0-30 bar) and temperatures (0-25 degrees C). The MCN-7 materials show excellent affinity towards CO2 molecules because of the strong acid base interactions. It is found that the amount of the CO2 adsorbed over the MCN-7 is mainly dependent on the BET surface area, and the structural order, and pore diameter of the adsorbent. MCN-7 with the highest specific surface area shows higher CO2 adsorption capacity than that of other materials including MCN with one dimensional structure. Crown Copyright (C) 2014 Published by Elsevier B.V. All rights reserved.