Alkali metal ion-exchanged ZSM-5 zeolites, M-ZSM-5 (M = Li, Na, K, Rb, and Cs), were prepared from Na-ZSM-5 by a conventional ion-exchange method, and their abilities to adsorb air were investigated through measurements of the amount of gases adsorbed as determined from elution curves on chromatography. The interaction of adsorbed gases and cations of M-ZSM-5 were examined from IR spectra of the adsorbed gases. It was found that the nitrogen in air was adsorbed selectively on M-ZSM-5 adsorbents, particularly Li-ZSM-5 and Na-ZSM-5 at room temperature. IR spectra indicated that nitrogen in air was adsorbed predominantly on cation sites in M-ZSM-5 zeolites owing to their strong interactions with these sites.