Crystal structure of a compact three-dimensional metal–organic framework based on Cs(+) and (4,5-di­cyano-1,2-phenyl­ene)bis­(phospho­nic acid)

A new metal–organic framework compound, poly[[μ(7)-dihydrogen (4,5-di­cyano-1,2-phenyl­ene)diphospho­nato]­(oxonium)caesium], [Cs(C(8)H(4)N(2)O(6)P(2))(H(3)O)](n) (I), based on Cs(+) and the organic linker 4,5-di­cyano-1,2-phenyl­ene)bis­(phospho­nic acid, (H(4)cpp), containing two distinct coordinating functional groups, has been prepared by a simple diffusion method and its crystal structure is reported. The coordination polymeric structure is based on a CsO(8)N(2) complex unit comprising a monodentate hydro­nium cation, seven O-atom donors from two phospho­nium groups of the (H(2)cpp)(2−) ligand, and two N-atom donors from bridging cyano groups. The high level of connectivity from both the metal cation and the organic linker allow the formation of a compact and dense three-dimensional network without any crystallization solvent. Topologically (I) is a seven-connected uninodal network with an overall Schäfli symbol of {4(17).6(4)}. Metal cations form an undulating inorganic layer, which is linked by strong and highly directional O—H⋯O hydrogen-bonding inter­actions. These metallic layers are, in turn, connected by the organic ligands along the [010] direction to form the overall three-dimensional framework structure.