As sustainable and clean energy, hydrogen is the most attractive and promising energy source in the future. Membrane separation is attractive due to its high hydrogen separation performance and low energy consumption. Van-der-Waals-corrected density functional theory (DFT) calculations are performed to investigate the hydrogen separation performance of 585 divacancy-defective germanene (585 germanene). It is found that the 585 germanene presents a surmountable energy barrier (0.34 eV) for hydrogen molecule passing through the membrane, and that membrane exhibits extremely high selectivity for H-2 molecules over CO, CO2, N-2, CH4 and H2S molecules in a wide range of temperatures. Meanwhile, the hydrogen permeance of 585 germanene can reach 1.94 x 10(-7) mol s(-1) m(-2) Pa-1 at the low limit temperature of methane reforming (at 450 K), which is higher than the industrially acceptable gas permeance. With high selectivity and permeance, the 585 germanene is a promising candidate for hydrogen separation. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.