Fig. 1
Three classes of 2D-enabled membranes: a Class 1 membrane with highly interlocked 2D nanosheets. b Class 2 membrane with interlocked 2D nanosheets that have intrinsic microporosity. Red arrow represents transport pathways through the external nanopores and yellow arrow represents transport pathways through the intrinsic nanopores. c Class 3 membrane with one- or layered membrane. d H2/CO2 separation performance (permeability and selectivity) of class 1 (graphene oxide [11, 157, 158], MXene [42], MoS2 [159]), Class 2 (2D ZIFs [80], 2D MOFs [84]), Class 3 [160], and 2D nanosheet based MMM [149, 161]. Straight red line refers to 2008 upper bound [162]