The invention concerns a zinc aluminate characterised in that it has, after calcination at 800 °C for 8 hours, a specific surface area of at least 85m2/g. The invention also concerns a precursor composition of said aluminate. The method for preparing the aluminate and the composition comprises the following steps: contacting in a solvent medium a salt, a zinc sol or alkoxide and an aluminium alkoxide; hydrolyzing the resulting mixture by adding an amount of water in excess relative to the aluminium alkoxide; recuperating the formed precipitate and optionally drying it, thereby obtaining the precursor composition; if required, calcining said precipitate, thereby obtaining the aluminate. Finally, the invention concerns the use of aluminate for treating motor vehicle exhaust gases.