Fig. 4: Membrane structure manipulation and proton conductivity evaluation.
From: Assembling covalent organic framework membranes with superior ion exchange capacity
a–c Effect of the n-octanoic acid addition amount on (a) thickness, (b) crystallinity, and (c) proton conduction performances of the TpBD-(SO3H)2 iCOFMs. Curves in (b) are the PXRD patterns of TpBD-(SO3H)2 iCOFMs fabricated with the n-octanoic acid addition amount of 5 mL (black), 10 mL (blue), 15 mL (purple), and 20 mL (red). In this experiment, 1.5 equivalents (eq) of sodium formate were added to the water phase as the amine monomer activator. d–f Effect of the sodium formate addition amount on (d) thickness, (e) crystallinity and (f) proton conduction performances of the TpBD-(SO3H)2 iCOFMs. Curves in (e) are the PXRD patterns of TpBD-(SO3H)2 iCOFMs fabricated with the sodium formate addition amount of 0.5 eq (black), 1.0 eq (orange), 1.5 eq (blue), 2.0 eq (red), 2.5 eq (purple), and 3.5 eq (green). In this experiment, 15 mL of n-octanoic acid were added to the organic phase as the aldehyde monomer activator. g Temperature-dependent proton conductivity of the TpBD-(SO3H)2 iCOFMs fabricated at optimized condition (the addition amount of n-octanoic acid and sodium formate was 15 mL and 1.5 eq, respectively). h IEC value versus proton conductivity for polymer membranes, previously reported iCOFMs and the TpBD-(SO3H)2 iCOFMs (detailed data was provided in Supplementary Table 9). i Proton-transfer activation energy (Ea) of the TpBD-(SO3H)2 iCOFMs fabricated at optimized condition. All the error bars in this figure represent the standard deviation (n = 3 independent experiments), data are presented as mean values ± SD.
