Fig. 2: Physical characterization of the COFs.

a FTIR spectra of TPBD, TPDBD, BD, DBD, and TP. b Partial unit structures of TPBD and TPDBD. c ¹³C CP-MAS solid-state NMR spectra of TPBD, TPDBD, and TP. d XPS C 1s spectra of TPBD, TPDBD, and TPDBD-CNa. e XPS O 1s spectra of TPBD, TPDBD, and TPDBD-CNa. f SEM image of TPDBD.