A three-dimensional (3D) cage-like organic network (3D-CON) structure synthesized by the straightforward condensation of building blocks designed with gas adsorption properties is presented. The 3D-CON can be prepared using an easy but powerful route, which is essential for commercial scale-up. The resulting fused aromatic 3D-CON exhibited a high Brunauer-Emmett-Teller (BET) specific surface area of up to 2247m(2)g(-1). More importantly, the 3D-CON displayed outstanding low pressure hydrogen (H-2, 2.64wt%, 1.0bar and 77K), methane (CH4, 2.4wt%, 1.0bar and 273K), and carbon dioxide (CO2, 26.7wt%, 1.0bar and 273K) uptake with a high isosteric heat of adsorption (H-2, 8.10kJmol(-1); CH4, 18.72kJmol(-1); CO2, 31.87kJmol(-1)). These values are among the best reported for organic networks with high thermal stability (ca. 600 degrees C).