“…Over the past decade, growing importance is being attached to the lamellar membranes with two-dimensional (2D) nanochannels for the elaborate design of next-generation separation membranes. − A series of 2D nanomaterials with atomic thickness and micrometer lateral dimensions, including graphene and graphene oxide (GO), , 2D transition metal carbides, carbonitrides or nitrides (MXene), transition metal dichalcogenides (TMDs), hexagonal boron nitride, layered double hydroxides, and those with well-designed microporosity, , have been strategically explored for the construction of lamellar membranes. The transport of molecules and/or ions in the lamellar membranes is routinely thought to occur in the confined space of nanochannels, where the microenvironment, such as channel size and chemical affinity, has a great impact on how the molecules and/or ions transfer. ,, In comparison with conventional inorganic membranes, 2D lamellar membranes show great potential in ion sieving, , oil and water separation, and water purification fields, , on account of easy large-scale fabrication, , preeminent mechanical and thermal properties, and high performance. , However, despite the extraordinary application prospects, there are still some unresolved issues limiting their practical applications in the field of gas separation, especially in CO 2 capture, which has elicited global concern . One is the undesired defects produced from nonuniform stacking of nanosheets, which often cause severe loss of selectivity at quite low concentration. , Another is the tiny difference of molecule dynamic diameter between CO 2 (0.33 nm) and N 2 (0.36 nm), which raises the difficulty of size-dependent separation and requires appropriate chemical affinity for selective adsorption and diffusion of CO 2 . , …”