Since the advent of the idea of ultrafiltration, microporous membranes have come through a long way in establishing a niche as an efficient technology for gas separation applications. More and more research is aimed at reducing pore size towards nanolevels, when separation factor is the criterion rather than the permeability. This work is focused at synthesizing and characterizing microporous inorganic membranes for gas separations by molecular sieving. BN was deposited on mesoporous vycor tubes using triethylamine borane complex (TEAB) and ammonia as precursors. Effect of temperature and deposition geometry on permeability of various gases has been studied. Very high selectivities have been achieved for separation of small inorganic gases such as He, H₂ from N₂. Activation energy study indicate that the permeability of He and H₂ are thermally activated with activation energies of 39.7 kJ/mol and 5O kJ/mol respectively. XRD analysis indicate an amorphous BN deposit in the vycor tube.