Abstract. The acid properties and catalytic activity of layered HNbMoO6 for liquid-phase Friedel–Crafts alkylation are examined. 31P MAS NMR spectroscopy using trimethylphosphine oxide as a probe molecule reveals that HNbMoO6 possesses strong acid sites in the interlayer region. Layered HNbMoO6 is demonstrated to display remarkable catalytic performance for this reaction, substantially ex…