During the past decade, interest has grown tremendously in the design and synthesis of crystalline materials constructed from molecular clusters linked by extended groups of atoms. Most notable are metal-organic frameworks (MOFs), in which polyatomic inorganic metal-containing clusters are joined by polytopic linkers. (Although these materials are sometimes referred to as coordination polymers, we prefer to differentiate them, because MOFs are based on strong linkages that yield robust frameworks.) The realization that MOFs could be designed and synthesized in a rational way from molecular building blocks led to the emergence of a discipline that we call reticular chemistry. MOFs can be represented as a special kind of graph called a periodic net. Such descriptions date back to the earliest crystallographic studies but have become much more common recently because thousands of new structures and hundreds of underlying nets have been reported. In the simplest cases (e.g., the structure of diamond), the atoms in the crystal become the vertices of the net, and bonds are the links (edges) that connect them. In the case of MOFs, polyatomic groups act as the vertices and edges of the net. Because of the explosive growth in this area, a need has arisen for a universal system of nomenclature, classification, identification, and retrieval of these topological structures. We have developed a system of symbols for the identification of three periodic nets of interest, and this system is now in wide use. In this Account, we explain the underlying methodology of assigning symbols and describe the Reticular Chemistry Structure Resource (RCSR), in which about 1600 such nets are collected and illustrated in a database that can be searched by symbol, name, keywords, and attributes. The resource also contains searchable data for polyhedra and layers. The database entries come from systematic enumerations or from known chemical compounds or both. In the latter case, references to occurrences are provided. We describe some crystallographic, topological, and other attributes of nets and explain how they are reported in the database. We also describe how the database can be used as a tool for the design and structural analysis of new materials. Associated with each net is a natural tiling, which is a natural partition of space into space-filling tiles. The database allows export of data that can be used to analyze and illustrate such tilings.

A series of metal-organic frameworks representing a non-interpenetrated framework analogue of MOF-14 have been synthesized by using two different linkers, 4,4',4''-benzene-1,3,5-triyl-benzoic acid (H(3)BTB) and 4,4'-bipyridine (Bpy). Interestingly, the transition metal ions in the paddle-wheel metal clusters could be exchanged by other transition metal ions via a direct single-crystal to single-crystal transformation. This post-synthesis route can be used for synthesis of isomorphous metal-organic frameworks that cannot be obtained by direct synthesis.

A comparative analysis of binary compounds and 61 simple anhydrous salts M(y)(LO(3))(z) (L = S, Se, Te, Cl, Br, I) was performed using the crystallochemical program package TOPOS. A topological similarity was found between the salts and six types of binary compounds (NaCl, NiAs, PoCl(2), Tl(2)S(2), ZnTe, rutile). It is notable that these structure relationships are typical for other groups of inorganic salts: borates, carbonates, nitrates, orthophosphates, orthoarsenates, sulfates, selenates, perchlorates, molybdates and halogenides of d-metals. For all the M(y)(LO(3))(z) compounds the topology and uniformity of the ion arrays were investigated. It has been established that in 36 out of the 61 salts at least one ion array has the topology of close packing or the body-centred cubic lattice. The results obtained have allowed us to come to conclusions about the structure-forming role of the arrays of various chemical composition.

Two open-framework germanates, SUT-1 and SUT-2, have been synthesized under hydrothermal conditions using ethylenediamine (en, H(2)NCH(2)CH(2)NH(2)) as templates and Ni(NO(3))(2)·6H(2)O as the transition-metal source. Their frameworks are built with Ge(10) clusters and [Ni(en)(2)](2+) complexes. In both structures, Ge(10) clusters form square nets in the a-c plane, while the [Ni(en)(2)](2+) complexes bridge the square nets via Ni-O-Ge bonds to form 3D networks. They present the first examples to incorporate Ni(2+) complexes into the germanate frameworks. In SUT-2, additional linkages by Ge(2)O(7) clusters between the square nets generate a new type of topology.

New building schemes of aluminophosphate molecular sieves from packing units (PUs) are proposed. We have investigated 61 framework types discovered in zeolite-like aluminophosphates and have identified important PU combinations using a recently implemented computational algorithm of the TOPOS package. All PUs whose packing completely determines the overall topology of the aluminophosphate framework were described and catalogued. We have enumerated 235 building models for the aluminophosphates belonging to 61 zeolite framework types, from ring- or cage-like PU clusters. It is indicated that PUs can be considered as precursor species in the zeolite synthesis processes.

Design of novel porous compounds is one of the fastest-growing fields of materials chemistry due to the broad range of applications including catalysis, adsorption, and separation. Open-framework germanates have shown large structure diversity and can form structures with extra-large pores. A systematic study of the structural features of the reported germanates is a key for the design of novel porous germanates. In this work, the topological study and classification of all known germanates that are built from Ge10(O, OH)27−28 (Ge10) or Ge7(O, OH, F)19 (Ge7) secondary building units, has been undertaken. We have demonstrated that the combination of topological technique and data mining provides new insights into structural chemistry of a group of compounds. We proposed an efficient and general strategy for prediction of novel structures in germanates and other chemical systems.

A novel 3D open-framework germanate, |N2C4H14|4 [Ge20O41(OH)6]·3H2O (SU-62), was prepared from hydrothermal synthesis using 1,4-diaminobutane as the organic structure directing agent (SDA). The crystal structure was solved by single crystal X-ray diffraction. The framework is built from Ge10(O,OH)27 (Ge10) secondary building units and exhibits an irregular three-dimensional channel system encircled by 10- and 14-rings. The framework of SU-62 has an underlying topology that follows a novel five-coordinated svh-5- I 4 1 / amd net, while the pores follow the tsi net. The thermal behavior of SU-62 was studied by thermogravimetric (TG) analysis and in situ X-ray diffraction (XRPD). Crystallographic data: orthorhombic, space group Fdd2, unit cell parameters a = 15.297(3) Å, b = 53.58(1) Å, c = 14.422(3) Å, V = 11821(4) Å3, Z = 8.

In this work we investigate the CoO(111)/Ni(111) interface by first-principles calculations, focusing on its structure and stability. To satisfy the approximate 5:6 ratio of the CoO and Ni lattice constants, we construct a supercell with 5 × 5 Co (O) and 6 × 6 Ni atoms per layer in the bulk regions. For the interface Ni layer and the adjacent Ni layer we consider different configurations and study the binding energy. We show for an ideal CoO interface terminated by 5 × 5 O atoms that the structure is more stable if there are 5 × 5 Ni atoms next to it instead of 6 × 6 as in the bulk. In addition, we observe that a transition layer with 31 or 33 Ni atoms located between the interface 5 × 5 Ni and bulk 6 × 6 Ni layers (which partially reflects the structures of both these layers) enhances the stability of the CoO/Ni interface. The electronic and magnetic modifications induced by the interface formation are discussed.