SF6 is widely used in gas-insulated equipment due to its high electrical insulation and arc extinguishing properties, but its strong greenhouse effect threatens the environment. Finding environmentally friendly alternative gases has become a challenge for the industry, and the C4F7N/CO2 gas mixture is the preferred alternative due to its excellent overall performance. During long-term operation of gas-insulated equipment, partial discharges or overheating occur due to insulation defects, resulting in decomposition of the insulating gas. By detecting the type and content of decomposed components, the insulation defects of GIS can be effectively detected. Therefore, in this study, based on the density functional theory, the molecular simulation software Materials Studio was used to construct the molecular models of the harmful decomposition gases C2N2 and CF4 of C4F7N/CO2 and MIL-101, which are commonly used as adsorbents for gas sensors, and the adsorption effects of MIL-101 on C2N2 and CF4 were analyzed according to the simulation results. The simulation results show that the adsorption of C2N2 by MIL-101 is larger than that of CF4 at the same pressure.