H2O Interaction with Solid H3PW12O40: An IR Study

The interactions of H 2 O with solid H 3 PW 12 O 40 have been studied by IR spectroscopy, and the results are compared with those obtained for H 2 O interacting with other acidic or superacidic solid systems (acidic zeolites and the perfluorosulfonic membrane H-Nafion). In fully dehydrated HPW a heterogeneous family of hydroxyls is evidenced which, by interaction with water, leads to the formation of neutral 1:1 H-bond adducts. At higher water pressures, the formation of symmetric diaquahydrogen ions, and of clusters of protonated water is also observed. The H 2 O···H + ···OH 2 symmetrical adducts are characterized by a very broad absorption in the 1400−700 cm - 1 range, which, by comparison with theoretical studies on gas-phase clusters and with experimental results obtained on H 5 O 2 + salts, is assigned to the νO···H + ···O mode. On the contrary, the IR spectra of fully dehydrated HPW do not show any absorption in this range.