A SAPO-34 membrane separated CO 2/H 2 and H 2/CH 4 mixtures at feed pressures up to 1.7 MPa. Strong CO 2 adsorption inhibited H 2 adsorption and decreased H 2 permeances significantly, especially at low temperatures, so that CO 2 preferentially permeated and CO 2/H 2 selectivities were higher at low temperatures. At 253 K, CO 2/H 2 separation selectivities were greater than 100 with CO 2 permeances of 3 × 10 −8 mol m −2 s −1 Pa −1. The CO 2/H 2 separation exceeded the upper bounds (selectivity–permeability plot) for polymer membranes. The SAPO-34 membrane separated H 2 from CH 4 because CH 4 is close to the SAPO-34 pore size and has a lower diffusivity than H 2. The H 2/CH 4 separation selectivity had a small maximum with temperature, and decreased slightly with feed pressure and CH 4 feed concentration.