<p>Bismuth-doped antimony tungstate (Bi-doped Sb₂WO₆) microspheres were synthesized via a novel hydrothermal synthesis approach. These microspheres were then used as active layers in gas sensors for the detection of carbon dioxide (CO₂), a significant greenhouse gas and a critical parameter for evaluating air quality. The incorporation of bismuth significantly enhances the gas-sensing performance of the Sb₂WO₆ microspheres, with the 4% Bi-doped sensing active layer achieving a remarkable response value of 15 when exposed to 200&#xa0;ppm of CO₂, outperforming the undoped Sb₂WO₆. Furthermore, the selectivity of the 4%Bi-Sb₂WO₆ sensor toward CO₂ gas was enhanced relative to the Sb₂WO₆ sensor. The fundamental mechanisms of gas sensing and the factors contributing to the improved CO₂ response of 4%Bi-Sb₂WO₆ microspheres were investigated using density functional theory. Bi-doped Sb₂WO₆ materials exhibit significant advantages in gas-sensing applications, including improved conductivity, enhanced gas adsorption capacity, increased reaction rates, good chemical stability, excellent selectivity, and the ability to adjust electron density. These characteristics enable Bi-doped Sb₂WO₆ to demonstrate higher sensitivity and rapid response capabilities in gas sensors, making it suitable for practical applications.</p> Graphical abstract <p></p>