The synthesis and crystal structure of UiO-19; an organically templated layered titanium phosphate with the ULM-11 topology

Abstract

An organically templated layered titanium phosphate, [TiOPO4]−[NH3(CH2)2NH2]+, has been synthesised under hydrothermal conditions. The crystal structure was determined from single-crystal X-ray diffraction. The layers of the two-dimensional structure consist of infinite corner-sharing chains of TiO5N octahedra cross linked by PO4 tetrahedra. The bonds to oxygen along the chain of titanium octahedra alternate between a short bond (1.719(1) A) and a long bond (2.150(1) A). One nitrogen of the diamine is directly coordinated to titanium while the other participates in hydrogen bonding to the subsequent anionic layer. The presence of TiIV in the compound is consistent with bond valence analysis, the observation of diamagnetic susceptibility and sharp signals in the solid state 31P NMR measurements. The compound is isostructural to the ULM-11 type of Fe-, Al-, V-fluorophoshates and identical to a titanium phosphate which had been assumed to contain TiIII.