The use of hydrate formation in porous media is an effective method for gas storage and separation. The equilibrium isotherms of CH4 and N-2 in CMK-3, a mesoporous carbon material, were measured under different tetrahydrofuran (THF) concentrations and temperatures. The higher is the temperature required, the greater is the formation pressure needed, but the presence of THF significantly reduces the hydrate formation pressure. When THF exists, both CH4 and N-2 form structure II (sII) hydrate; however, the amount of hydrate generation is lower than the theoretical value. As the operating pressure increases, some of the sII CH4 hydrate may transform into structure I (sI) and the amount of hydrate generation increases. The desorption isotherms showed that the gas hydrate decomposed completely when the operating pressure was below the hydrate decomposition pressure. In addition, it is feasible to separate gas mixtures via hydrate formation using the different gas hydrate formation pressures.