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Adsorption isotherms of pure gases present in flue gas including CO2, N2, SO2, NO, H2S, and water were studied using prussian blues of chemical formula M3[Co(CN)6]2·nH2O (M = Co, Zn) using an HPVA-100 volumetric gas analyzer and other spectroscopic methods. All the samples were characterized, and the microporous nature of the samples was studied using the BET isotherm. These materials adsorbed 8−10 wt % of CO2at room temperature and 1 bar of pressure with heats of adsorption ranging from 200 to 300 Btu/lb of CO2, which is lower than monoethanolamine (750 Btu/lb of CO2) at the same mass loading. At high pressures (30 bar and 298 K), these materials adsorbed approximately 20−30 wt % of CO2, which corresponds to 3 to 5 molecules of CO2per formula unit. Similar gas adsorption isotherms for SO2, H2S, and NO were collected using a specially constructed volumetric gas analyzer. At close to 1 bar of equilibrium pressure, these materials sorb around 2.5, 2.7, and 1.2 mmol/g of SO2, H2S, and NO. In particular, the uptake of SO2and H2S in Co3[Co(CN)6]2is quite significant since it sorbs around 10 and 4.5 wt % at 0.1 bar of pressure. The stability of prussian blues before and after trace gases was studied using a powder X-ray diffraction instrument, which confirms these materials do not decompose after exposure to trace gases.