Treatment of germanium dioxide with a 33% aqueous solution of 1,2-diaminopropane (DAP) under solvothermal conditions leads to the formation of colourless octahedral crystals of the novel germanate (1,2-DAPH 2 ) 2 Ge 9 (OH) 4 O 18 · 2 H 2 O. The compound crystallises in the orthorhombic space group Pbca, a = 14.4155(10), b = 12.9384(9), c = 14.5417(8) Å,V =2712.2 (3) Å 3 ; Z =4. The structure consists of an anionic [Ge 9 (OH) 4 O 18 ] 4− framework with isolated [1,2-DAPH 2 ] 2+ cations and water molecules in the channels of the structure. The primary building units of the anionic framework are GeO 4 tetrahedra, GeO 5 trigonal bipyramids, and GeO 6 octahedra. The asymmetric unit consists of two GeO 5 units sharing a common edge to form a Ge 2 O 8 unit. This Ge 2 O 8 unit is corner-linked to two GeO 4 tetrahedra, and finally one GeO 4 tetrahedron is connected to a GeO 6 octahedron by cornersharing. The connectivity yields a chain-like Ge 5 O 19 fragment as a secondary building unit (SBU). The chain fragments are interconnected with each other forming the three-dimensional framework. Three types of channels with diameters ranging from 5.98 to 8.025 Å intersect the three-dimensional germanate network. Upon heating the compound decomposes in three steps starting at about 125˚C losing the water and the 1,2-diaminopropane molecules. In situ X-ray diffraction experiments show that the water molecules are removed retaining the integrity of the skeleton of the material. The removal of H 2 O is accompanied with an anisotropic shrinkage of the structure. The original lattice parameters were obtained after the uptake of water.