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We have performed comprehensive topological analysis of 2-periodic coordination networks in 10 371 metal–organic compounds. Both local and overall topologies of complex groups were determined, classified, and stored in the electronic databases. Two plane nets, square lattice (sql) and honeycomb (hcb), were found to compose two-thirds of all the coordination networks. Strong correlations were found between local topological characteristics (coordination numbers of atoms or complex groups, coordination figures, formalized coordination modes of ligands and coordination formula) and the overall topology that in many cases allowed us to predict possible topological motifs from the data on chemical composition with high probability. The possibility to develop an expert system that could envisage local and overall topology of periodic coordination networks is discussed, and an example is given of how such a system can work.

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273 metal-organic frameworks (MOF) with entanglements of two-periodic structural groups (layers) were found by a comprehensive analysis of the Cambridge Structural Database using the program package TOPOS [1]. 163 Parallel and 108 inclined catenated layers were observed and in only in one case both modes of entanglement are realized together. TOPOS tools were applied to consider simplified representations of the structural groups as nets, where the nodes correspond to metals and/or centers of gravity of polydentate ligands. The most widespread type of topology of the layers in the simplified nets is the square net 44-sql (161 compounds); 65 MOFs have the topology of the honeycomb net 66-hcb; the third place is occupied by the topology 4.82-fes (13 cases). A strong correlation was found between the coordination type of ligand, the coordination number of central atom and the global topology of the net. Thus, in 146 compounds with the underlying topology of the square net, metal is connected to four bridge ligands. Out of them, in 122 compounds all the bridge ligands are bidentate, and in 83 compounds metal has coordination number six being connected to four bidentatebridge and two monodentate dangled ligands. Among the compounds with the honeycomb type of topology the most frequent local topology is formed by three bidentate-bridge and two bidentate terminal (coordination number of metal is seven). It was shown, that the results obtained can be used to design the crystals containing tangled two-periodic structural groups.