One-dimensional aminated titania nanotubes were prepared by a facile distillation-precipitation polymerization method and were incorporated into sullonated poly(ether ether ketone) (SPEEK) to fabricate mixed matrix membranes (MMMs). The aminated titania nanotubes (TNT-FM) with abundant amine groups increased the CO2-facilitated transport sites in MMMs. Moreover, the CO2-facilitated transport pathways (CO2-FTP) were constructed from aminated titania nanotubes in polymer matrix, and acted as the fast CO2 transport channels to transfer CO2 molecules continuously and smoothly. Water uptake and water state in MMMs also played an important role in the gas separation performance. The relationship between the water content and CO2 separation performance was investigated. Nanotubes as fillers showed water retention properties during water evaporation from the MMNs at low humidity. The highest ideal selectivities of the SPEEK/TNT-IM MMMs for CO2/CH4 and CO2/H-2 were 56.8 and 62.0, respectively, with a CO2 permeability of 2090 Barrer. (C) 2015 Elsevier B.V. All rights reserved.