Isolated hafnium (Hf) sites were prepared on Silicalite-1 and SiO2 investigated for acetone conversion to isobutene. Characterization by IR, 1H MAS NMR, UV-vis spectroscopy suggests that Hf atoms are bonded the support via three O have one hydroxyl group, i.e, (?SiO)3Hf-OH. In case of Hf/Silicalite-1, Hf-OH groups hydrogen bond with adjacent Si-OH form (?SiO)3Hf-OH···HO-Si? complexes. The turno...