MIL-101 is a promising adsorbent because of its large pore volume, high separation selectivity, easy regeneration, and good stability. MIL-101 was synthesized and characterized by X-ray diffraction, scanning electron microscopy, and nitrogen adsorption at 77 K. Adsorption isotherms of pure N-2, CH4, and CO2 were measured on MIL-101 from 263 K to 313 K and at pressures up to 0.8 MPa. The Langmuir model was a good fit for the experimental isotherms and the isosteric heats of adsorption decreased in the order: CO2 > CH4 > N-2. The CO2/CH4 separation selectivity was sensitive to the adsorption pressure and temperature and it varied from 3.2 to 6.3. In contrast, the CH4/N-2 separation selectivity changed from 2.6 to 3.3 with temperature and pressure.