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Metal-organic frameworks (MOFs) have been examined extensively for CO2 capture, and the influence of water co-adsorption on these processes is particularly relevant, as CO2 capture generally occurs in humid gas streams. To investi-gate CO2/H2O co-adsorption, binary adsorption isotherms of CO2 and H2O were measured on MOF-808-TFA (TFA = trifluoro-acetic acid). When water was pre-adsorbed on MOF-808-TFA, and a subsequent CO2 adsorption isotherm was measured, the CO2 adsorption was slightly reduced, as expected. However, when CO2 was adsorbed first and then an H2O adsorption iso-therm was measured, no significant H2O adsorption capacity was observed. The near complete loss of water adsorption ca-pacity was observed even when only a trace amount of CO2 was pre-adsorbed. The results show that unexpected, non-state function adsorption equilibria can result from dynamic MOF behaviors and defect sites, which may lead to counterintuitive adsorption data compared to traditional materials.