Developing new materials for energy and environment-related applications is a critical research field. In this context, organic and metal–organic framework (MOF) materials are a promising solution for sensing hazardous gases and saving energy. Herein, a flexible membrane of the zeolitic imidazole framework (ZIF-67) mixed with a conductivity-controlled chitosan polymer was fabricated for detecting hydrogen sulfide (H2S) gas at room temperature (RT). The developed sensing device remarkably enhances the detection signal of 15 ppm of H2S gas at RT (23 °C). The response recorded is significantly higher than previously reported values. The optimization of the membrane doping percentage achieved exemplary results with respect to long-term stability, repeatability, and selectivity of the target gas among an array of several gases. The fabricated gas sensor has a fast response and a recovery time of 39 s and 142 s, respectively, for 15 ppm of H2S gas at RT. While the developed sensing device operates at RT and uses low bias voltage (0.5 V), the requirement for an additional heating element has been eliminated and the necessity for external energy is minimized. These novel features of the developed sensing device could be utilized for the real-time detection of harmful gases for a healthy and clean environment.