Keggin-type polyacid clusters on apatite: characteristic catalytic activities in solvent-free oxidation

Abstract We found that Keggin-type phosphometalates are effective catalysts for solvent-free oxidation with urea–H 2 O 2 by dispersing on fluorapatite solid phase. In the solid phase system the phosphomolybdate (NH 4 ) 3 PMo 12 O 40 was more effective than the phosphotungstate (NH 4 ) 3 PW 12 O 40 , whereas the latter was much superior to the former in the liquid-phase reaction with aqueous H 2 O 2 . In situ formation of novel peroxo-type species from (NH 4 ) 3 PMo 12 O 40 /FAp and urea–H 2 O 2 , which may lead to the high catalytic activity in the solid phase system, was observed by 31 P solid-state NMR.