A series of water-tolerant Lewis acidic TiO2/Nb2O5 center dot nH(2)O heterojunction catalysts with different Ti : Nb ratios have been prepared and investigated in the conversion of glucose into HMF in water. Under optimized conditions (i.e. 150 degrees C, 300 min), 5-hydroxymethylfurfural (HMF) was obtained in 42% yield together with formic acid (FA) in 17% yield. Extending the reaction time, the yield of FA can be increased to over 60%, albeit at the expense of HMF which is reduced to nH(2)O catalyst also shows high activity in the conversion of cellobiose and potato starch into HMF. The catalyst is stable and can be reused several times with only a slight decrease in activity.