for 50 min. Data of heat flow and pressure-time dependence were collected throughout the whole measurement run, thus allowing calculation of the differential heat of adsorption as a function of adsorbed amount for each step. Coverage was calculated based on the amount of adsorbed co2 and the total amount of Bronsted acid OH groups in the sample, as determined from the zeolite chemical composition and further checked by IR spectroscopic titration with pyridine and acetonitrile.