Two dumbbell-shaped porous gamma-graphynes were designed by substituting one-third acetylenic linkages with heteroatoms nitrogen and hydrogen named gamma-GYN and gamma-GYH, respectively. The calculated cohesive energies and phonon dispersion spectra indicate the possibility to realize the new membranes in experiments. The separation performance of the designed monolayers for H-2 from H2O, CO2, N-2, CO, and CH4 was investigated using both first-principle density functional theory (DFT) and molecular dynamic (MD) simulations. The DFT calculations suggest the designed membranes are excellent in H-2 separation because of the super high selectivities of H-2 over other gases H2O, CO2, N-2, CO, and CH4 (>10(10) 10(13), 10(21), 10(18), and 10(46), respectively, at room temperature) together with the high/extremely low permeances for H-2/other gases, e.g., reaching the industrial standard at 400 K (gamma-GYN) and 425 K (gamma-GYH)/lower than the industrial limit by 3-22 orders even at 600 K. The MD simulations indicates that only H2 in the gas mixture containing H-2, H2O, CO2, N-2, CO, and CH4 can penetrate across the membranes even at the temperature of 600 K and gamma-GYN is more favorable for H-2 penetration. All these results indicate both the designed membranes, especially gamma-GYN, are excellent candidates for H-2 purification from gas mixtures. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.