MICROPOROUS inorganic materials such as zeolites find widespread application in heterogeneous catalysis, adsorption and ion-exchange processes. The rigidity and stability of such frameworks allow for shape- and size-selective inclusion of organic molecules and ions(1-4). Analogous microporous structures based on organic building blocks have the potential for more precise rational design, through control of the shape, size and functionalization of the pores(5-8). Here we report the synthesis of a metal-organic framework designed to bind aromatic guest molecules selectively. The basic building block is a symmetric organic molecule, which binds metal ions(9,10) to form layers of the metal-organic compound alternating with layers whose composition is determined by the functionalization of the starting molecules. The layers create channels in which guest aromatic molecules may be selectively bound, We show that the crystal lattice thus formed is thermally stable up to 350 degrees C, even after removal of included guest molecules, and that the inclusions can be selectively readsorbed.