Covalent assembly of a two-dimensional molecular "sponge" on a Cu(111) surface: confined electronic surface states in open and closed pores.

We present a new class of on-surface covalent reactions, formed between diborylene-3,4,9,10-tetraaminoperylene and trimesic acid on Cu(111), which gives rise to a porous 2D-'sponge'. This aperiodic network allowed the investigation of the dependence of electron confinement effects upon pore size, shape and even in partial confinement.