Gas sensing properties of silicon carbide monolayers with extended line defects

Silicon-based two-dimensional materials offer a promising platform for tunable gas-sensing interfaces, where defect topology governs electronic response and adsorption dynamics. Here, we use density functional theory to investigate a silicon carbide (SiC) monolayer containing a 585 extended line defect (ELD) with carbon interstitials, focusing on its interaction with CO, NO, and SO molecules. The ELD activates localized electronic states that enhance surface reactivity, enabling well-defined adsorption configurations and measurable charge redistribution for all studied gases. CO exhibits moderate binding and ultrafast room-temperature recovery, indicating excellent reversibility and selectivity. NO and SO display stronger electronic coupling to the defect region, producing distinct charge-transfer signatures that may be advantageous for applications requiring persistent molecular tagging or operation in environments where stable adsorption is desired. Mechanical strain and alternative adsorption geometries preserve these qualitative trends, underscoring the robustness of the defect-engineered surface. Overall, the results highlight ELD-functionalized SiC as a versatile 2D interface whose defect-driven electronic landscape can be tailored for selective detection strategies across different classes of gas molecules.