The aim of the present work is to examine whether these same conclusions hold for macrocycles that assemble into porous frameworks in the solid state. For example, the [18]annulene molecule (Fig. ) packs in such a way that the π system of one monomer lies atop the pore of the neighboring monomer, in a form of offsetstacking. The boron-based covalent organic framework (COF) material known as COF-1, 15 a truncated Fig. : Monomers examined in the present work, with an indication of the pore size for each: (a) benzene, (b) [18]annulene, (c) porphyrin, (d) COF-1. Gray atoms are carbon, white are hydrogen, blue are nitrogen, red are oxygen, and pink are boron.