Aziridine-Functionalized Mesoporous Silica Membranes on Polymeric Hollow Fibers: Synthesis and Single-Component CO2 and N2 Permeation Properties

The synthesis of aziridine-functionalized mesoporous silica membranes On polymeric hollow fibers is described, and their single-component CO2 and N-2 permeation properties are investigated under both dry and humid conditions to elucidate the unusual permeation mechanisms observed in these membranes. Hollow fiber-supported mesoporous silica membranes are amine-functionalized with aziridine to yield hyperbranched aminopolymers within the membrane pores. The effects of the hyperbranched polymers in the mesopores on gas transport properties are investigated by single-component gas permeation measurements. The hyperbranched aminosilica membrane shows counterintuitive N-2-selective (over CO2) permeation during operation under dry conditions. Further characterization of the permeation behavior reveals the effects of strong adsorption of CO, under dry permeation conditions, leading to reduced CO2 diffusivity because of CO2-induced amine cross-linking in the mesopores. On the other hand, the hyperbranched aminosilica membrane shows CO2-selective properties under humid conditions. Water molecules cause a lower degree of amine cross-linking and thus allow facilitated transport of CO2. This first study of hollow fiber-supported hyperbranched aminosilica membranes indicates that they can be tuned to have N,- or CO2-selective permeation properties under the conditions employed.