Extended metal-organic frameworks Members: Sandra Arcediano, Garikoitz Beobide, Oscar Castillo, Fabio Scé, Javier Cepeda, Mónica Lanchas, Antonio Luque, Sonia Pérez, Pascual Román, Jintha Thomas and Daniel Vallejo Introduction: Metal–organic frameworks (MOFs) are a class of hybrid materials comprising metal ion-based vertices and organic ligands (linkers) that serve to connect the vertices into two or three-dimensional periodic structures. The structures and properties of MOFs can be carefully tailored by judicious selection of metal ion and organic linker building blocks. A hallmark property of MOFs is their intrinsic porosity, which renders them potentially useful for gas storage, separations, catalysis, and a variety of additional applications that rely on highly specific host–guest interactions. Their promising properties coupled with the ease by which their structures can be modified make MOFs one of the most exciting, diverse, and rapidly growing areas of modern chemistry research. Detailed research lines: A. Design of new metal-nucleobase (MBioFs and supraMBioFs) porous materials, it makes use of the coordinative versatility of the nucleobases to act as bridging ligands and their ability to establish strong supramolecular interactions. Examples of such materials are scarce, especially in the case of supraMBioFs, although these are more economical than those MOFs obtained through complicated connector- ligands.[Coord. Chem. Rev. 2013, 257, 2716] Focusing on the synthesis of the scarce supraMBioFs (only one example published by us: CrystEngComm 2011, 13, 3301), the synthetic strategy to achieve this goal is the use of building blocks consisting of discrete metal complexes where the nucleobase is attached to the metal center by at least two donor atoms. The geometric constraints achieved among the coordinated nucleobases that this coordination mode imposes are otherwise difficult to obtain, specially the non-coplanar disposition of the nucleobase synthon groups. Given that multiple hydrogen bonding donor/acceptor positions are accessible, these discrete entities may assemble together by means of double or triple complementary hydrogen bonds to generate a supramolecular solid. Porosity comes from the previously mentioned geometric constraints that hinder an effective packing of the metal- nucleobase entities leading to the presence of great voids in the crystal structure.