Acid gases (e.g.,
NO
x
and SO
x
), commonly found in complex chemical and petrochemical
streams, require material development for their selective adsorption
and removal. Here, we report the NO
x
adsorption
properties in a family of rare earth (RE) metal–organic frameworks
(MOFs) materials. Fundamental understanding of the structure–property
relationship of NO
x
adsorption in the
RE-DOBDC materials platform was sought via a combined experimental
and molecular modeling study. No structural change was noted following
humid NO
x
exposure. Density functional
theory (DFT) simulations indicated that H2O has a stronger
affinity to bind with the metal center than NO2, while
NO2 preferentially binds with the DOBDC ligands. Further
modeling results indicate no change in binding energy across the RE
elements investigated. Also, stabilization of the NO2 and
H2O molecules following adsorption was noted, predicted
to be due to hydrogen bonding between the framework ligands and the
molecules and nanoconfinement within the MOF structure. This interaction
also caused distinct changes in emission spectra, identified experimentally.
Calculations indicated that this is due to the adsorption of NO2 molecules onto the DOBDC ligand altering the electronic transitions
and the resulting photoluminescent properties, a feature that has
potential applications in future sensing technologies.
We report on the
availability and chemical utility of primary amines within metal–organic
frameworks (MOFs) for cell targeting. Primary amine groups represent
one of the most versatile chemical moieties for conjugation to biologically
relevant molecules, including antibodies and enzymes. Specifically,
we used two different chemical conjugations schemes, utilizing the
amino functionality on the organic linker: first, carbodiimide chemistry
was used to link the primary amine to available carboxyl groups on
the protein neutravidin; second, sulfhydryl cross-linking chemistry
was used via Traut’s reagent scheme. Importantly, this is the
first report that documents this methodology implemented with MOF
systems. Finally, the ability of the EpCAM antibody targeted MOFs
to bind to a human epithelial cell line (A549), a common target for
imaging studies, was confirmed with confocal microscopy.
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