Formation of Subnanometer Zr-WOx Clusters within Mesoporous W–Zr Mixed Oxides as Strong Solid Acid Catalysts for Friedel–Crafts Alkylation

WO 3 –ZrO 2 mixed metal oxides is an important class of acid solid. Here, we successfully synthesized a variety of mesoporous WO 3 –ZrO 2 mixed metal oxides by a well-controlled sol–gel process (AcHE) using Zr(OBu) 4 and WCl 6 as the inorganic precursors in the presence of poly block copolymer F127. Their structures and acid properties have been well characterized by XRD, Raman, N 2 adsorption measurement, and HRTEM analyses. In addition, new insights from TG-DSC and 31 P NMR characterization also provide useful information on the formation of strong acidity of this important solid acid. Moreover, their structure-to-properties relationship has been studied in the Friedel–Crafts (F–C) reaction of anisole and benzyl alcohol. We identified that the subnanometer WOx clusters act as the most active sites for the F–C reaction. Most importantly, we show that the formation of these subnanometer WOx clusters can be rationally controlled. It is shown that a minimum W concentration (0.07 at the calcination temperature of 800 °C) and a minimum calcination temperature (650 °C at a given W concentration of 0.1) are required during the preparation of these acid catalysts for the development of highly active subnano WOx clusters.