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Keywords:

  • heterogeneous catalysis;
  • NMR spectroscopy;
  • proton mobility;
  • solid heteropolyacids;
  • solid state
Thumbnail image of graphical abstract

Flip and hop before you′re caught! The proton dynamics of solid 12-tungstophosphoric acid (TPA) is probed by solid-state 2H NMR in a temperature range from 293–503 K. Protons of TPA are shown to be involved in two types of molecular motion (see picture): the anisotropic local two-site flipping between the two possible orientations of the O[BOND]H bond at bridged oxygens of the Keggin anion, and the isotropic diffusion by hopping between neighboring surface oxygens of the anion.