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The Supporting Information is available free of charge on
remove a mixture of thirteen PFAS (Figure S18) with
different chain lengths and functional groups at envi-
ronmentally relevant concentrations (Figure 3, Figure
S21–S22). Following exposure of nanopure water solu-
tions containing 1 µg L–1 (1 ppb) of each PFAS to 10 mg
L–1 of each COF, equilibrium binding was observed
within 30 minutes, and each COF exhibited broad spec-
trum removal and high affinity for nearly all of the
PFAS. Among the three COFs, 28%[NH2]–COF per-
formed the best and removed more than 90% of 12
PFAS and 63% of perfluorobutanoic acid (PFBA). These
observations suggest that 28%[NH2]–COF has the
highest affinity for 13 PFAS compared to 1%[NH2]–
COF and 100%[NH2]–COF, consistent with the GenX
studies performed at higher concentration. We also ob-
served that the 1%[NH2]–COF and 100%[NH2]–COF
exhibited partial desorption of the bound PFAS between
the 1- and the 24- hour time points. This effect was less
pronounced for 28%[NH2]–COF (Table S7). Partial
desorption was also observed in experiments conducted
only with GenX (Figure S15), ruling out competitive
adsorption as an explanation. We are currently investi-
gating the nature of these effects, which indicate a slow,
dynamic change to these COFs that is not observed in
the 28%[NH2]–COF adsorbent. Finally, we bench-
marked the GenX adsorption by 28%[NH2]–COF
against a granular activated carbon (GAC, particle size
>1000 µm) and a powdered activated carbon (PAC, par-
ticle size 10–75 µm) at environmentally relevant con-
centrations (Figure 3c). 28%[NH2]–COF outperformed
both GAC and PAC in these experiments, in which GAC
removed 0%, PAC removed 72%, and 28%[NH2]–COF
removed 91% of GenX after 30 min. These combined
observations indicate that amine-functionalized 2D
COFs are outstanding candidates for GenX and broad-
spectrum PFAS removal.
the ACS Publications website. Experimental procedures,
characterization, additional PFAS adsorption experiments
(PDF)
AUTHOR INFORMATION
Corresponding Authors
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Notes
Northwestern University and Cornell University have filed
a provisional patent based on these findings.
ACKNOWLEDGMENTS
The study was supported by the Strategic Environmental
Research and Development Program (ER18-1026). It made
use of the IMSERC at Northwestern University, which has
received support from the Soft and Hybrid Nanotechnology
Experimental (SHyNE) Resource (NSF ECCS-1542205);
the State of Illinois and International Institute for Nano-
technology (IIN), and the Keck-II facility and the EPIC
facility of Northwestern University’s NUANCE Center,
which have received support from SHyNE Resource (NSF
ECCS-1542205); the MRSEC program (NSF DMR-
1720139) at the Materials Research Center; IIN; the Keck
Foundation; and the State of Illinois.
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In conclusion, we incorporated a varying density of
amine functionalities into the pores of imine-linked
COFs while maintaining high surface areas ( ≥ 1000
m2/g). The amine-functionalized COFs show rapid up-
take and high affinity for adsorbing GenX and other
PFAS that is strongly influenced by the amine loading.
Among the amine-functionalized imine COFs,
20%[NH2]–COF showed the highest uptake of GenX at
high concentrations ([GenX]0 = 0.2 and 50 mg L–1) and
28%[NH2]–COF showed the most rapid and the highest
uptake of GenX and twelve other PFAS at environmen-
tally relevant concentrations, suggesting that the ideal
composition of amines for removing PFAS is in this
range. The well-defined COF structure and relationships
between amine loading and PFAS binding also suggest
general design criteria to improve the performance of
other adsorbent classes.
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