We have developed new asymmetric high-
Tc superconducting (Bi
1.85Pb
0.35)Sr
1.9Ca
2.1Cu
3.1O
10+ membranewith high efficiency for nitrogen separation from air. This membrane with controlled pore structure canbe prepared by the electrophoretic deposition of colloidal (Bi
1.85Pb
0.35)Sr
1.9Ca
2.1Cu
3.1O
10+ nanosheets onthe substrate pellet. The presence of mesopores in the asymmetric membrane plays an important role inachieving high gas selectivity through the enhancement of magnetic interaction between the superconductormembrane and oxygen molecules. Also, we have found that the control of experimental factors like theorientation of magnetic field, temperature, and pressure difference across the sample is of specialimportance in optimizing the gas selectivity of the membrane. The present results underscore theapplicability of the superconductor membrane as a gas separation device.