The integrity of the graphene membranes transferred directly in the module was examined by gas permeation studies (setup shown in Figure ). As-synthesized CVD graphene, without the oxidation step, yielded a low CO2 permeance of 29 GPU with a CO2/N2 ideal selectivity of 15.6, consistent with the literature on intrinsic vacancy defects in graphene, confirming that cracks were avoided during transfer (Table ). Successful crack-free transfer was also obtained from assynthesized graphene transferred to the 5 cm 2 and 50 cm 2 cross-flow modules (Table ). This establishes the robustness of this novel crack-free transfer approach in preparing large-area PG membranes. SEM images of commercial polyethersulfone (PES) support (d) and stainless steel (SS) mesh (e). The insets are pictures of the two supports. f, Pictures of stacked membrane assembly hosting Cu/PG/MRF/PES/SS mesh (panels i and ii), etching setup for Cu (panel iii), and as-prepared graphene membrane module after etching Cu foil (panel iv). g-i, Optical (g), and SEM (h, i) images of graphene surface after removal of Cu. j-k, A ~8 × 12 cm 2 graphene coupon (j) is cut into 24, 2 × 2 cm 2 small coupons (k). l, All 24 coupons in panel (j) lead to successful 1 cm-scale membranes. Half of the membrane modules were assembled with transparent cover plates to reveal the sealing.