Nanocomposite membrane based on polydimethylsiloxane (PDMS) and nanoscale SiO2 particles were prepared by a convenient and mild sol-gel copolymerization of tetraethoxysilane as well as cross-linking reaction. The oxygen-enriching properties of cross-linking PDMS/SiO2 nanocomposite membranes containing different silica conversion and SiO2 contents were investigated. The results showed that the nanocomposite membranes exhibited good membrane-forming ability, superior mechanical properties, and high solvent resistance as well as excellent oxygen-enriching properties for air purification. The oxygen-enriching performance was regulated by the organic/inorganic ratio and silica conversion in the sol-gel synthesis process. Permeability and selectivity could increase simultaneously with the addition of nanoscale SiO2. The oxygen permeation coefficient of the nanocomposite membrane increased to 680 Barrer and oxygen/nitrogen separation factor kept 3.0 or so, both higher than those of the corresponding pure PDMS membrane. The high oxygen-enriching properties of the nanocomposite membranes arose from the introduction of SiO2 particles, the sol-gel copolymerization, and cross-linking method. (C) 2012 American Institute of Chemical Engineers AIChE J, 59: 650-655, 2013