Multidimensional nanochannel design and regulation of ultra-thin GOQDs-AGQDs composite membranes

Graphene-based composite membranes with long and tortuous transport paths restricted its efficient and wide application in substance separation and purification field. In this study, we propose a multidimensional mass-transfer channel construction method for fabricating highly permeable 2D laminar membranes with lots of stable molecular transport channels. In particular, a robust GOQDs-AGQDs composite membranes with adjustable interlayer sieving channels were prepared based on vacuum assisted self-assembly by intercalating AGQDs with average size of 7.5 nm between GOQDs with average size of 34.0 nm, which presented highly permeability with plentiful nano-channels in both vertical and horizontal directions. As the mass fraction of doped AGQDs reached to 60 wt%, the best performance of GOQDs-AGQDs composite membranes was obtained, with a functional layer thickness of 24.1 nm, good stability, and strong acid and alkali resistance. The usage of small diameter GOQDs with intercalating smaller diameter AGQDs extremely shortened the transfer channel path and slightly increased the interlayer spacing (8.26 to 8.75 Å), which dramatically improved its permeation flux of 14 times higher than that of the pure GO membrane with similar dye rejection, and reached to 133.3 L·m−2·h−1 under 2 bar at the optimized condition. This study provided insights into self-assembling small-sized 2D nanomaterials into membranes and fine-tuning their nanochannel structure.