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 2247 m  g . More importantly, the 3D-CON displayed outstanding low pressure hydrogen (H , 2.64 wt %, 1.0 bar and 77 K), methane (CH , 2.4 wt %, 1.0 bar and 273 K), and carbon dioxide (CO , 26.7 wt %, 1.0 bar and 273 K) uptake with a high isosteric heat of adsorption (H , 8.10 kJ mol ; CH , 18.72 kJ mol ; CO , 31.87 kJ mol ). These values are among the best reported for organic networks with high thermal stability (ca. 600 °C).