To achieve enhanced CO2/N-2 separation performance, 1,3,5-benzenetricarboxylic acid (H3BTC) was utilized in polymer composite membranes. Since H3BTC has three carboxylic acids on the benzene ring, the separation performance was expected to be enhanced by the synergistic effect of (1) the increased solubility of CO2 by dipole-dipole interactions between CO2 and carboxyl groups in H3BTC and (2) the barrier effect of H3BTC on the transport of N-2. Actually, when H3BTC was incorporated into poly(vinylpyrrolidone) (PVP), the selectivity of CO2/N-2 increased to 8.5 with a CO2 gas permeance of 1.2 GPU, while the neat PVP did not show separation performance. The chemical and physical behaviors of H3BTC in PVP were further investigated by FT-IR and TGA analyses. (C) 2015 Elsevier B.V. All rights reserved.