The pyrochlores (H 3 O) x Sb x Te (2-x) O 6 (x = 1, 1.1 and 1.25) obtained by ion exchange from K x Sb x Te (2-x) O 6 oxides were used as catalysts for the conversion of fructose to 5-hydroxymethylfurfural (HMF) in H 2 O/Methyl isobutyl ketone (MIBK). The structure of the resulting compounds as well as the location of the H 3 O + units inside the three-dimensional network, were determined by XRD from powder samples. The effect of factors such as reaction time and temperature on the formation of HMF was studied. A fructose conversion of 99% and a yield of 59% were achieved after 120 min of reaction time and at 150°C temperature. The percentage of substitution of the cations Sb and Te in the position B of the pyrochlore was determinant to achieve the maximum incorporation of H 3 O + ions in the pyrochlore structure, which allowed to correlate the density of acidic sites present in the materials and their catalytic activity.