The surface modification of poly[1-(trimethylsilyl)propyne] (PTMSP) film via a thiol-ene click reaction with sodium 3-mercapto-1-propanesulfonate has yielded membranes having a CO2 permeance as high as 530 GPU with a CO2/N-2 selectivity of 21. This level of performance, together with the simplicity of this surface modification, suggests that such materials could become viable alternatives to some of the most promising membrane materials that are currently being explored for the practical capture of CO2 from flue gas.