Bridging the materials and pressure gaps: The adsorption of CO on ZnO surfaces becomes much stronger in the presence of preadsorbed CO$_2$. The increased strength of the interaction between CO and polycrystalline ZnO powder originates from the formation of tridentate carbonate species on the mixed-terminated ($10\overline{1}0$) surfaces, which increase the Lewis acidity of neighboring Zn$^{2+}$ cations.