An organic compound, a three-dimensional organic structure formed by using the organic compound, a separation sieve and an optical layer having the organic structure, and an optical device having the optical layer as an optical amplification layer are provided. The organic structure includes a plurality of organic molecules self-assembled by non-covalent bonding. Each of the unit organic molecules has an aromatic ring, a first pair of substituents being connected to immediately adjacent positions of substitutable positions of the aromatic ring, and a second pair of substituents being connected to immediately adjacent positions of remaining substitutable positions of the aromatic ring. The unit organic molecules are self-assembled by van der Waals interaction, London dispersion interaction or hydrogen bonding between the first and the second pairs of the substituents and by pi-pi interactions between the aromatic rings.