Synthesis and Structure Determination of a New Organically Templated Scandium Fluorophosphate Framework and Its Indium Analogue

Two new isostructural scandium and indium phosphate frameworks, (C₆H₁₄N₂)M₄F₂(PO₄)₄·4H₂O (M = Sc, In), have been synthesized from hydrothermal conditions using an organic amine, 1,4-diazabicyclo[2.2.2]octane (DABCO), as a template. Their structures have been determined by single-crystal X-ray diffraction and supported by solid-state magic-angle spinning (MAS) NMR spectroscopy. They crystallize in the P2₁/n space group with a = 10.283(2) Å, b = 12.698(2) Å, c = 17.864(3) Å, and β = 102.761(3)° and a = 10.280(2) Å, b = 12.700(2) Å, c = 17.860(4) Å, and β = 102.47(3)° for Sc- and In-compounds, respectively. They are built from corner-sharing M octahedra and P tetrahedra which form eight- and six-membered channels along the b-axis. The channels are occupied by organic templates and water molecules. All PO₄ groups share four corners with M polyhedra, resulting in a fully connected framework. The local environments around P, F, and Sc atoms in the Sc-compound were carefully examined by ³¹P MAS, ¹⁹F MAS, ⁴⁵Sc MAS, ⁴⁵Sc MQMAS, and ⁴⁵Sc/¹⁹F REDOR NMR spectroscopy.