The third challenge relates to fabricating large-area PG membranes while avoiding cracks in graphene. Cracks typically manifest during the transfer of CVD graphene from the Cu foil to porous support or during pressurization of the PG membrane. Wafer-scale and roll-to-roll transfer have been demonstrated in fabricating graphene devices for electronic applications. However, while these applications are tolerant to macroscopic cracks in graphene, gas separation membranes are not. Crack-free PG is essential for selective transport between similar-sized gas molecules such as CO2 and N2 under pressurized conditions. Centimeter-scale PG membranes have been demonstrated for nanofiltration after stitching cracks using interfacial polymerization. However, this approach has not been demonstrated for gas separation. We have shown that cracks in PG can be avoided by using gas-permeable mechanically reinforcing support film (MRF).