Ultrathin, molecular sieving membranes composed of microporous materials offer great potential to realize high permeances and selectivities in separation applications, but strategies for their production have remained a challenge. Here we show a route for the scalable production of nanometre-thick metal–organic framework (MOF) molecular sieving membranes, specifically via gel–vapour deposition, which combines sol–gel coating with vapour deposition for solvent-/modification-free and precursor-/time-saving synthesis. The uniform MOF membranes thus prepared have controllable thicknesses, down to ~17 nm, and show one to three orders of magnitude higher gas permeances than those of conventional membranes, up to 215.4 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ for H₂, and H₂/C₃H₈, CO₂/C₃H₈ and C₃H₆/C₃H₈ selectivities of as high as 3,400, 1,030 and 70, respectively. We further demonstrate the in situ scale-up processing of a MOF membrane module (30 polymeric hollow fibres with membrane area of 340 cm²) without deterioration in selectivity.

This review presents and discusses the remarkable progress of GO membranes, especially the strategies and mechanisms for controlling their transport pathways in liquid separation.