The purification of natural gas and the removal of carbon dioxide from flue gases are crucial to economize precious resources and effectively relieve a series of environmental problems caused by global warming. Metal-organic framework (MOF) materials have demonstrated remarkable performance and benefits in the area of gas separation; however, obtaining materials with high gas capacity and selectivity simultaneously remains difficult. In addition, harsh synthesis conditions and solvent toxicity have been restricted in large-scale production and industrial application. Therefore, MOF-801(Zr/Ce/Hf) was created based on the green synthesis of the MOF-801 construction unit by altering the kinds of metal salts, and the impact of three metal nodes on the performance of gas adsorption and separation was demonstrated by contrasting the three MOFs. The results showed that MOF-801(Ce) has the best CO2 adsorption capacity (3.3 mmol/g at 298 K), which also was demonstrated with in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results, CO2/CH4 (ideal adsorbed solution theory (IAST) = 13.28 at 298 K, 1 bar, CO2/CH4 = 1:1, v/v), and the separation performance of CO2/N2 (IAST = 57.46 at 298 K, 1 bar, CO2/N2 = 1:1, v/v) among the group. Green synthesis of MOF-801(Zr/Ce/Hf) is an ideal candidate for flue gas separation and methane purification because of its high regeneration capacity and strong cyclic stability.