Porphyrin Frameworks: Network Crystals

Many biological systems use porphyrin molecules for important processes and are similarly used by scientists to improve the properties of their materials. Porphyrin molecules used as building units to construct porphyrinic frameworks (PFs) are discussed in this article. Several examples which have been characterized by single-crystal X-ray diffraction are described and include metal-metalloporphyrinic frameworks that are assembled using coordinate-covalent bonds or by directional supramolecular interactions (noncovalent and noncoordinative interaction, NCMPFs). Introductions and applications are discussed to provide a guide for future PF research to improve upon properties such as molecular sorption, light harvesting, and heterogeneous catalysis. The discussion is limited and will not include porphyrin molecules that have been trapped as guests in porous materials such as metal-organic frameworks. Further perspectives on PF applications will come with more research and are envisioned to replicate naturally occurring phenomena.