A new family of phosphate oxynitrides was prepared by nitridation of an amorphous zirconophosphate precursor under ammonia flow. The oxygen substitution by nitrogen modified the acid-base properties of the zirconophosphate oxynitrides obtained. Surface acidity decreased sharply when bulk nitrogen content increased while basic properties as measured by SO2 adsorption calorimetry greatly depended on the O/N ratio. At 50 degrees C, the Knoevenagel condensation of benzaldehyde with malononitrile in toluene brings an 80% of conversion after 5 h.