A sorbent suitable for sorbing aldehydes includes acidified zeolite impregnated with a urea-based compound, the acidified zeolite having a pore opening of 5 Å or greater and a molar ratio of silicate to aluminate of at least 1.1:1. The sorbent may be prepared by impregnating acidified zeolite with a solution of a urea-based compound, where the acidified zeolite includes proton counterions. The sorbent may be supported on a filter support to provide an air filter.