AbstractIn this paper we discuss a novel approach to the band gap engineering of semiconductors Si, Ge, GaAs and AIN. We suggest that nanoporous polymorphs of these materials may exist which would offer a significant variation of the electronic band gap. Structurally, nanoporous semiconductors are related to the zeolitic nets, and a systematic procedure of generating these structures from the (4;2) nets is described. We use the ab initio total energy quantum molecular dynamics method Fireball96 to investigate the energetics and the electronic properties of these nanoporous or “expanded” semiconductor phases.