CO2 is one of the main components of air, accounting for 0.03–0.04% (300–400 ppm) of the total volume of the atmosphere. CO2 gas is chemically stable and is an inert gas, which makes the means of detecting it extremely limited. To overcome these challenges, in this paper, nanoscale M-MOF-74 (M=Mg, Ni, Zn, Co) was synthesized by a facile method in a two-hour reaction at room temperature, which combined with a quartz crystal microbalance (QCM) sensor-enabled the detection of CO2 gas at room temperature. The CO2 sensing performance of M-MOF-74 coated QCM sensors at room temperature was systematically investigated. The experimental results showed that the Mg-MOF-74 sensor responded to 2000 ppm CO2 at room temperature with 66, and at the same time, had good linearity, high response/recovery (75 s/50 s), and good selectivity to CO2. The electrical parameters and quality factor of the QCM were further verified by impedance analysis. In addition, the potential CO2 adsorption mechanism may be mainly related to the open metal sites in the Mg-MOF-74 material and the synergistic effect of Mg-O bonds. This work confirms that the M-MOF-74 material provides a new avenue for QCM CO2 sensing, and the sensor is expected to be a potential candidate for CO2 detection.