Robust assembly of aromatic molecules Organic materials can exhibit high porosity, but the structures often collapse or decompose at high temperatures. Yamagishi et al. synthesized an aromatic molecule that bears a symmetrical outer shell of three dipyridylphenyl wedges and crystallized it from highly dielectric solvents. Porous crystals formed with complex pore-wall structures that resulted from labile C–H⋯N bonds and van der Waals forces. Despite the weakness of these interactions, the porous structure was stable up to 202°C and could be recovered after collapse by exposure to solvent vapor. Science , this issue p. 1242