The reasonable allocation and control of CO₂ concentration in a greenhouse are very important for the optimal growth of crops. In this study, based on density functional theory (DFT), an MoS₂–GeSe monolayer was proposed to unravel the issues of the lower selectivity, poorer sensitivity and non-recyclability of traditional nanomaterial gas sensors. The incorporation of MoS₂ units greatly enhanced the sensitivity of the pure GeSe monolayer to CO₂ and the high binding energy also demonstrated the thermal stability of the doped structures. The ideal adsorption energy, charge transfer and recovery time ensured that the MoS₂–GeSe monolayer had a good adsorption and desorption ability. This paper aimed to solve the matter of recycling sensors within agriculture. This research could provide the theoretical basis for the establishment of a potentially new generation of gas sensors for the monitoring of crop growth.