Abstract: | When {2,2′‐(2‐methyl‐2‐nitropropane‐1,3‐diyl)diimino]diacetato}copper(II), Cu(C8H13N3O6)], (I), was crystallized from a binary mixture of methanol and water, a monoclinic two‐dimensional water‐ and methanol‐solvated metal–organic framework (MOF) structure, distinctly different from the known orthorhombic one‐dimensional coordination polymer of (I), was isolated, namely catena‐polycopper(II)‐μ3‐2,2′‐(2‐methyl‐2‐nitropropane‐1,3‐diyl)diimino]diacetato] methanol 0.45‐solvate 0.55‐hydrate], {Cu(C8H13N3O6)]·0.45CH3OH·0.55H2O}n, (II). The monoclinic structure of (II) comprises centrosymmetric dimers stabilized by a dative covalent Cu2O2 core and intramolecular N—H...O hydrogen bonds. Each dimer is linked to four neighbouring dimers via symmetry‐related (opposing) pairs of bridging carboxylate O atoms to generate a `diamondoid' net or two‐dimensional coordination network. Tight voids of 166 Å3 are located between these two‐dimensional MOF sheets and contain a mixture of water and methanol with fractional occupancies of 0.55 and 0.45, respectively. The two‐dimensional MOF sheets have nanometre‐scale spacings (11.2 Å) in the crystal structure. Hydrogen‐bonding between the methanol/water hydroxy groups and a Cu‐bound bridging carboxylate O atom apparently negates thermal desolvation of the structure below 358 K in an uncrushed crystal of (II). |