Cyclodextrin tuned interlayer spacing in covalent organic framework membranes for efficient dye/salt separation

Covalent organic framework (COF) membranes assembled by top-down approach often suffer from low permeance due to pore sheltering effect between adjacent COF nanosheets. Herein, COF membrane with tunable interlayer spacing is fabricated using cyclodextrin (CD) as intercalator for efficient dye/salt separation. The intercalation of CD can increase the interlayer spacing between adjacent COF nanosheets to decrease mass transport resistance. Accordingly, water can transport through both the intrinsic pores of COF nanosheets and the interlayer nanochannels, and the water flux of the COF/CD membrane is increased to 160 +/- 8 L m- 2 h- 1, which is four times higher than that of COF membrane, with high rejection (>95.9 %) for dyes of molecular weight exceeding 327 g mol- 1. Meanwhile, the COF/CD membrane exhibits rejection of 99.7 % for alcian blue 8GX (AB) and rejection of 11.1 % for NaCl in the AB/NaCl solution. This study offers a facile way to tune the interlayer spacing in COF membranes for diverse chemical separations.