By using microporous polyacrylonitrile (PAN) hollow fibers as the substrate, we developed two types of composite fibers for air-separation. One was a poly(4-vinyl pyridine) (4-PVP)/(hexafluoro propane dianhydride)-durene(6FDA)/PAN composite hollow fiber, and the other was a 6FDA-3,5-diaminobenzonitrile/6FDA-durene/PAN composite hollow fiber. The asymmetric PAN fiber was prepared using dry-jet wet-spinning technology, and the deposition of a thin gutter layer of 6FDA-durene on PAN was carried out by prewetting PAN fibers with Fluorinert(R) before solution coating. The topcoating of a thin layer (200-300 angstrom) of PVP or 6FDA-3,5-diaminobenzonitrile on PAN/6FDA-durene fibers was conducted using a conventional solution coating method. The selectivity of 0.7% 4-PVP/2% 6F-durene/PAN composite fibers for O2/N2 was 5.6 with an O2, permeance of 32.2 X 10(-6) cc (STP)/cm2 s cmHg, whereas the selectivity of 0.5% 6FDA-3,5-diaminobenzonitrile/2% 6F-durene/PAN fibers was 5.1 with an O2 permeance greater than 37.2 X 10(-6) cc (STP)/cm2 s cmHg. Both fiber selectivities can be further improved by increasing the thicknesses of the selective layer.