Covalent
organic frameworks (COFs) are penetrated with uniform
and ordered nanopores, implying their great potential in molecular/ion
separations. As an imine-linked, stable COF, TpPa-1 is receiving tremendous
interest for molecular sieving membranes. Theoretically, atomically
thin TpPa-1 monolayers exhibit extremely high water permeance but
unfortunately no rejection to ions because of its large pore size
(∼1.58 nm). The COF monolayers tend to stack to form laminated
multilayers, but how this stacking influences water transport and
ion rejections remains unknown. Herein, we investigate the transport
behavior of water and salt ions through multilayered TpPa-1 COFs by
nonequilibrium molecular dynamics simulations. By analyzing both the
interfacial and interior resistance for water transport, we reveal
that with rising stacking number of COF multilayers exhibit increasing
ion rejections at the expense of water permeance. More importantly,
stacking in the offset eclipsed fashion significantly reduces the
equivalent pore size of COF multilayers to 0.89 nm, and ion rejection
is correspondingly increased. Remarkably, 25 COF monolayers stacked
in this fashion give 100% MgCl2 rejection, whereas water
permeance remains 1 to 2 orders of magnitude higher than that of commercial
nanofiltration membranes. This work demonstrates the rational design
of fast membranes for desalination by tailoring stacking number and
fashion of the COF monolayers.
A fluorescent probe (N-(4-methyl-2-oxo-2H-chromen-7-yl)-2,4-dinitrobenzenesulfonamide), which exhibits high selectivity to glutathione and cysteine among amino acids including sulphur-containing methionine and metal ions, was synthesized. The experiments demonstrate that the fluorescent probe is a reliable and specific probe for glutathione and cysteine in living cells.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.