Porous organic networks (PONs) are an emerging class of organic materials with 2D and 3D architectures formed by covalent bonds between light elements, such as C, H, N, O, and B. Extensive efforts have been devoted to synthesizing thermally "stable" 3D PONs to realize their practical applications. Here, the design and synthesis are reported for two new 3D PONs with fused aromatic structures. The PONs structures are constructed by the double condensation reaction between tetrapodal octaamine and pyrenetetraketone (PTK) or hexaketocyclohexane (HKH) to produce PTK-PON (P-PON) or HKH-PON (H-PON), respectively. The prepared nitrogen-rich PONs show good thermal stabilities with specific surface areas of 873 m(2) g(-1) (P-PON) and 741 m(2) g(-1) (H-PON). Because of their relatively narrow pore dimensions (1.29 and 0.78 nm, respectively), the synthesized PONs exhibit high adsorption performance for small molecules such as carbon dioxide (CO2), hydrogen (H-2), methane (CH4), and iodine (I-2).