Accurate Structural Description of the Two Nanoporous Fluorinated Aluminophosphates ULM-3(Al) and ULM-4(Al) by Solid-State NMR

Abstract

This work reports an investigation of the localization of F atoms and OH groups in the two fluorinated aluminophosphates ULM-3(Al) and ULM-4(Al) by multinuclear and multidimensional high-resolution solid-state magic-angle spinning nuclear magnetic resonance (NMR) spectroscopy. First, in ULM-3(Al), we show that the compound is fully fluorinated. A whole set of state-of-the-art homonuclear and heteronuclear 2D NMR experiments (19F–31P, 19F–19F, 31P–31P, 27Al–31P, and 1H–31P) have been recorded, yielding a unique line assignment of all the 31P and 19F resonances to the corresponding crystallographic sites. In a second part, ULM-4(Al) is shown to be a quite remarkable sample because it contains both fully and partially fluorinated building units. The structural differences between ULM-3(Al) and ULM-4(Al) are finally discussed in the light of the results in terms of potential templating role of water.