Periodic mesoporous organosilica (PMO) is a special type of ordered mesoporous silica, in which organic moieties are integrated into the silica framework to form hybrid organic-inorganic material. In this work, we successfully incorporate T-type large sized melamine based triorganosilsesquioxane as organic linker in the periodic mesoporous organosilica. Melamine-bridged PMOs were prepared with high reproducibility by co-condensation using N2,N4,N6-tris(3-(triethoxysilyl) propyl)-1,3,5-triazine-2,4,6-triamine (TBTS) and sodium metasilicate in the presence of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer (Pluronic P123, EO(20)PO(70)EO(20), Aldrich) at high acidic concentration. The resulted melamine PMO had well-ordered p6mm hexagonal mesostructure and played a role as an efficient catalyst for carbon dioxide activation in the coupling of propylene oxide with CO(2). The adsorption behavior of carbon dioxide at the GGA-RPBE level of DFT was explored as a first step towards new mechanistic pathways for CO(2) activation over metal-free catalyst. (C) 2010 Elsevier B.V. All rights reserved.