The N 2 and O 2 sorption was studied on synthetic and natural mordenites, and on molecular sieves 4A, 5A and 13X. The sorption dynamics was characterized by frequency response rate spectra, determined at 133 Pa, 195 or 298 K. The rate of sorption step governed the mass transport in all powder samples (particles size <0.063 mm), except in 4A, wherein the micropore diffusion was the rate-determining slowest step. In larger granules ($1.4-2.0-mm size), the diffusion resistance of the macro-and mesopores controlled the rate of transport. Under comparable conditions the mass transport of O 2 was always faster than that of N 2 . The adsorption-induced vibration spectra of N 2 and O 2 were examined by DRIFT spectroscopy in the range of 1-7 bar and 298-393 K. DRIFT spectra were used to determine the isosteric heat of adsorption (Q a ) on the energetically homogeneous 5A sample. The Q a of N 2 and O 2 adsorption was 23.5 and $10.1 kJ/mol, respectively. In general, relative to the gas-phase Raman frequency, blue-shifted m NN and redshifted m OO bands were obtained. However, N 2 adsorption on Na-mordenites resulted in a blue-and a red-shifted m NN band. Blue-shifted bands were assigned to adsorption in end-on orientation, i.e., with molecular axis parallel to the direction of the electric field of the adsorption site Na þ cations. The red-shifted m NN band suggests that some nitrogen molecules, probably those, linked to Na þ cations in the side pockets of the mordenite main channel, were forced by spatial constraints in orientation, inclined to the direction of the electric field.