In this work, we have studied the (N2, H2, O2, NO, NO2, CO, CO2, SO2, H2S, H2O, and NH3) gases adsorption properties on the O-vacancy-containing Sc2CO2 monolayer by first-principles calculations. We have determined the preferred adsorption positions and the structural features of the O-vacancy-containing Sc2CO2 monolayer after adsorption of different gas molecules. The adsorption energy and charge transfer from the monolayer to the gas molecules have been calculated. The calculated results show

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... that H2, N2, NH3, H2S and H2O molecules are physisorbed, while CO2, CO, NO2, NO, O2 and SO2 molecules are chemisorbed in the neighboring area of the O-vacancy of the Sc2CO2 monolayer. The existence of the O-vacancy significantly enhances the CO and CO2 adsorption intensity of the defect Sc2CO2 monolayer compared to the original Sc2CO2 monolayer. Our results show that the O-vacancy-containing Sc2CO2 monolayer can be used for detecting NO gas as a resistive sensor.