Fig. 2: Characterization of X-CPDs-n.

a TEM images of X-CPDs-3. b Size distributions of X-CPDs-n (n = 2–8). c XRD patterns of CMX and X-CPDs-n (n = 2–8). d 13C NMR spectra of X-CPDs-n (n = 2–8) (500 MHz, D2O). e FTIR spectra of X-CPDs-n (n = 2–8). f XPS survey spectra of X-CPDs-3. g High-resolution XPS C1s spectrum of X-CPDs-3.