Molecular intercalated graphene oxide with finely controllable interlayer spacing for fast dye separation.

Molecular intercalation has been widely used for graphene oxide (GO) nanosheets to control interlayer spacing (d -spacing). However, further research is necessary to refine and enhance the precision of d -spacing control. In this study, we demonstrate a versatile strategy to create chitosan (CS) intercalated GO (GO@CS) nanosheets, whose d -spacing can be finely controlled by numbers of linked CS unit. This means the concentration of CS solution directly influences d -spacing of GO, and we can get the desired d -spacing for various applications by modulating the CS concentration. This is benefited from the linear structure of CS ensuring a consistent molecular length. The simulation of molecular structures with different numbers of linked CS unit supports this model. Then, the nanofiltration membranes prepared by these GO@CS nanosheets show high hydrophilicity, strong chemical bonding force, and abundant negative charges, which enhances permeability (water permeance of 91 L m−2 h−1 bar−1), stability, and anti-fouling ability during dye separation processes, even though they are ultrathin (∼70 nm). Notably, the contrasting filtration efficiencies observed for oppositely charged dye molecules indicate a great potential use in molecular sieving. [Display omitted] • A versatile strategy is used for chitosan intercalated graphene oxide nanosheets. • Interlayer spacing is finely controlled by numbers of linked chitosan unit. • Laminar membranes have good hydrophilicity and tunable surface charge. • Membranes have high water permeance of 91 L m-2 h-1 bar-1 and dye rejection of 95 %. • Membranes show various filtration efficiencies of oppositely charged dye molecules. [ABSTRACT FROM AUTHOR]