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Compared with MoS 2 monolayer, the SV-MoS 2 monolayer improves the absorbability toward SF 6 decomposition products and increases the selectivity of SO 2 F 2. [Display omitted] • The investigation about sulfuric vacancy in two-dimensional molybdenum disulfide monolayer. • The adsorption behavior of typical SF 6 decomposition components on SV-MoS 2 monolayer is shown. • The physical sensing properties and mechanism of adsorption system are fully analyzed. A long-running SF 6 insulating gas decomposes without being detected in time would cause incalculable consequences, therefore, real-time monitoring towards SF 6 status is of practical significance. Currently, the gas-sensitive properties of two-dimensional materials are the focus and hotspot of gas sensor research, however, in practical situations, material preparation and device fabrication will inevitably bring about defects. Therefore, the effects of sulfuric vacancy (SV) in molybdenum disulphide are proposed and explored, and a comparative study of gas-sensitive properties (pristine MoS 2 vs SV- MoS 2) is carried out using density functional theory based on the first principles. Constructing typical adsorption models for SF 6 decomposition components on monolayer, together with analyzing the optimum adsorption structures, adsorption energy, density of states, molecular orbitals, electrical conductivity and co-adsorption behaviors. The results show that the SV brings a defective state to MoS 2 monolayer, which contributes to an overall increase in the adsorption energy for the decomposition components (the increase > 0.15 eV), making the undifferentiated adsorption effect selective for SO 2 F 2. The physical interaction between the decomposition products and SV-MoS 2 monolayer is more favorable for desorption. These results indicate it is appropriate for detecting SF 6 status in high-voltage insulation environments, with pointers to practical applications for two-dimensional materials. [ABSTRACT FROM AUTHOR]