One step microwave-assisted synthesis of nanocrystalline WOx-ZrO2 acid catalystsElectronic supplementary information (ESI) available: Experimental section (synthesis protocols and characterization techniques). Characterization of the materials and catalytic results not shown in the manuscript. See DOI: 10.1039/c6cy01082b

Nanocrystalline ZrO 2 and WO x -ZrO 2 catalysts with good control over the zirconia phase and the nature of the W species were synthesized by a microwave-assisted aqueous route. The monoclinic ZrO 2 (m-ZrO 2 ) and tetragonal ZrO 2 (t-ZrO z ) polymorphs were isolated through accurate control of the synthetic conditions, in acidic and basic media, respectively. The evolution of the zirconia and W species under annealing of the WO x -ZrO 2 nanocomposites at 500 °C and 800 °C was studied, and the resulting materials were tested as catalysts for aldoxime dehydration and hydration of alkynes for the production of nitriles and carbonyls, respectively. In the dehydration reaction, the most active species are W( vi ) in tetrahedral coordination, independently of the ZrO 2 polymorph, while in the hydration reaction the zirconia phase plays a key role, as the tungsten doped t-ZrO 2 appears to be the most active catalyst. One-step microwave synthesis allows one to tune WO x species and ZrO 2 polymorphs showing different activities in acid reactions.