3D–2D–0D Stepwise Deconstruction of a Water Framework Templated by a Nanoporous Organic–Inorganic Hybrid Host

Abstract

The supramolecular salt [H(2)pip](3)[Ge(hedp)(2)].14H(2)O (1) [H(2)pip(2+)=piperazine cation C(4)H(12)N(2)(2+); hedp(5-)=deprotonated form of etidronic acid, C(2)H(3)P(2)O(7)(5-)) is reported. This consists of an organic-inorganic hybrid hydrogen-bonded nanoporous framework, the internal surface of which acts as a template for the three-dimensional (3D) clustering of water molecules. The structure and molecular dynamics of this material are characterised by single-crystal X-ray diffraction, thermogravimetric analysis, Raman (H/D isotopic substitution) spectroscopy, and (2)H solid-state (wide-line and MAS) NMR spectroscopy. Material 1 is shown to be unusual because 1) few nanoporous materials exhibit a well-organised 3D framework of water molecules, 2) it provides a unique opportunity to follow experimentally and to rationalise the deconstruction of a 3D water framework and 3) despite the fact that the hybrid framework is a supramolecular salt, the structure does not collapse after dehydration and the final material is crystalline.