F-gases, such as NF3, CF4, and SF6, are strong greenhouse gases, and their emissions to the atmosphere should be prevented. We investigated F-gas separations by carbon molecular sieve (CMS) as a strong candidate for reduction of greenhouse gas. The viscosity of the precursor solution (Matrimid5218 (R)) was controlled from 10 cP to 40 cP for fabricating defect-free thin polymer films on porous supports, and thermal pyrolysis protocols were subsequently optimized in order to produce high-performance membranes. CMS membranes pyrolyzed at 650 degrees C in high-purity He (99.9999%) exhibited the best performance for N-2/NF3 separation (650 N-2 GPU, N-2/NF3 = 26.6). As compared with polymeric membranes, the CMS membranes performed far outperformed especially because of their high N-2 permeance, which originated from the thickness of the thin film along with the rationally controlled micropores. Therefore, these high-flux CMS membranes are expected to provide high productivity when implemented in large-scale processes for F-gas separation and recovery. (C) 2015 Elsevier B.V. All rights reserved.