Two-dimensional sub-nanometer confinement channels enabled by functional carbon dots for ultra-permeable alcohol dehydration

Graphene oxide (GO) membranes have shown great promise in pervaporation dehydration of biofuels, expected to satisfy the demand of lower energy consumption. However, the swelling of interlayer spacing between GO nanosheets in aqueous environment, usually leads to deteriorated membrane separation performance and limited stability. Here, we report ultra-permeable sulfonated carbon quantum dots (SCDs)/GO composite membranes that are designed through strategically introducing the functional quasi-spherical nanoparticles - SCDs as water transport promoters and crosslinker into GO laminates. Well self-assembly stacked manner between SCDs and GO nanosheets created highly hydrophilic two-dimensional sub-nanometer confinement interlayer channels for fast water transport, while the crosslinking effect between SCDs and GO nanosheets producing a stable microstructure to maintain GO interlayer spacing against swelling. Furthermore, the SCDs occupied the vacancies around the ordered edges of GO nanosheets also resulted in an enhancement of water selective permeation. The microstructure evolution was confirmed by low-field nuclear magnetic resonance spectra. The prepared SCDs/GO membrane on polyethersulfone (PES) substrate with ∼150 nm selective layer exhibited a total flux of 5.88 kg m−2 h−1 and water/butanol separation factor of ∼4407 at 343 K, which outperforms the performance of state-of-the-art membranes reported to date. Meanwhile, the thin composite membrane showed long-term operation stability for 130 h when fed with 90 wt% butanol/water solution. This research provides a promising method for the selective water separation of high-performance GO membranes.