Fig. 3: Characterizations of chemical, crystalline, and pore structures of COF membranes.
From: Covalent organic framework membranes for efficient separation of monovalent cations
a 13C MAS NMR spectra. The peaks corresponding to C=O and C–N were detected at ~185 ppm and 150 ppm for COFs membranes, revealing the existence of keto-structures within the membranes. b XRD pattern. Two signals can be observed in 2 theta of 5° and 27–27.5° attributed to crystalline planes of (100) and (001), respectively, manifesting the high crystallinity of COF membranes. c Pore size distribution. The average channel size of membranes concentrated on 1.33−1.34 nm. d Schematics of COF membranes with TpPa main skeletons. The COF membranes had well-defined 1D channels and even-distributed acid groups along the channels. e 2D-GIWAXS spectra. Signal corresponding to (100) plane set near qxy = 0 whereas signal referring to (001) plane concentrates on qz = 0, showing the in-plane distribution of 1D hexatomic-ring channel perpendicular to the membrane surface. f water contact angle of COF membranes. g QCM spectra of COF membranes. Source data are provided as a Source Data file.
