Sulfated zirconia having a BET surface area of 90 m(2) g(-1) and a temperature-resistant mesoporous texture was prepared by thermolysis (at 1000 K) of zirconium sulfate. Infrared studies of surface sulfates, CO adsorption at 77 K, and room temperature adsorption of pyridine showed close similarity to sulfated zirconias prepared by impregnation or doping from the gas phase. Four main families of Lewis acid centers were found, which gave CO adducts characterized by stretching frequencies of 2212, 2202, 2196, and 2188 cm(-1). Interaction of CO (at liquid nitrogen temperature) with surface face hydroxyls (in partially hydroxylated samples) was found to shift the O-H stretching frequency from 3650 to 3510 cm(-1), due to formation of hydrogen-bonded OH ... CO complexes. This downward shift, Delta nu(OH) = 140 cm(-1), is significantly larger than the corresponding value for pure zirconia (Delta nu(OH) = 90 cm(-1)), which strongly suggests enhancement of the Bronsted acidity. Samples showing the acidic OH group at 3650 cm(-1) were found to contain also disulfate groups and traces of molecular water. Surface hydroxyls in sulfated zirconia still appear, however, to be weaker Bronsted acid sites than are bridging OH groups in zeolites.