MXene-intercalated covalent organic framework membranes for high-flux nanofiltration.

Covalent organic framework (COF) membranes are envisioned as promising materials for precise molecular separations. The manipulation of interlayer spacing to offer additional mass transfer channels in COF membranes may be an effective way towards high-flux separation processes but still challenging. Herein, the COF membranes with 1D/2D mixed-dimensional channels are explored by the intercalation of MXene for high-flux dye separations. Thereinto, porous TpPa-SO 3 H nanosheets offer the 1D in-plane channels, and smaller-sized Ti 3 C 2 T x -NH 2 nanosheets serve as the intercalators to generate 2D interlayer channels. By tuning the content of Ti 3 C 2 T x -NH 2 , the interlayer spacing is enlarged from 0.32 nm to 0.46 nm, affording low diffusion energy barrier and ultrafast diffusion kinetics. Compared to the pristine TpPa-SO 3 H membrane, the COF/Mx-8 membrane exhibits an 90 % increase in water flux to 375.8 L m−2 h−1 bar−1, while maintaining high rejections toward various dye molecules. The strategy of MXene-intercalated mixed-dimensional channels is suitable for diverse types of 2D COF membranes. A mixed-dimensional channel strategy is developed by interlayer intercalation for fabricating high-flux COF membranes towards nanofiltration. The 1D in-plane channels and 2D interlayer channels are constructed simultaneously by actively manipulating interlayer-enlarging effect and pore-blocking effect, which affords significantly improved water flux. [Display omitted] • Interlayer manipulation is implemented in COF membranes by the intercalation of MXene nanosheets, affording mixed-dimensional channels. • The 2D interlayer spacing can be enlarged from 0.32 nm to 0.46 nm while maintaining the 1D in-plane channel size above 1.21 nm. • Compared with the pristine TpPa-SO 3 H membrane, the COF/Mx-8 membrane exhibits an 90 % increase in water flux to 375.8 L m−2 h−1 bar−1. • The strategy of MXene-intercalated mixed-dimensional channels is suitable for other types of 2D COF membranes. [ABSTRACT FROM AUTHOR]