The adsorption behavior of energy-related gases onto ZIF-8 was investigated using terahertz waves. Comparison of the terahertz transmission spectra of ZIF-8 before and after exposure to the gases revealed that the 2 THz vibrational mode was involved in the gate-opening motion of organic linker molecules. The adsorption properties of each gas were detailed by monitoring the intensities of the 2 THz absorption peak.