TY - JOUR
T1 - Role of modulators in controlling the colloidal stability and polydispersity of the UiO-66 metal-organic framework
AU - Morris, William
AU - Wang, Shunzhi
AU - Cho, David
AU - Auyeung, Evelyn
AU - Li, Peng
AU - Farha, Omar K.
AU - Mirkin, Chad A.
N1 - Funding Information:
This material is based upon work supported by Air Force Office of Scientific Research (AFOSR) award FA9550-14-1-0274, the U.S. Army award W911NF-15-1-0151, and the Vannevar Bush Faculty Fellowship program sponsored by the Basic Research Office of the Asst. Secretary of Defense for Research and Engineering and funded by the Office of Naval Research grant N00014-15-1-0043. O.K.F. acknowledges DTRA for financial support (HDTRA1-14-1-0014). PXRD data were collected at the Dupont-Northwestern-Dow Collaborative Access Team (DND-CAT) Beamline 5-IDD at Argonne National Laboratory. Use of the DNA-CAT beamline was supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, under contract DE-AC02-06CH11357.
Publisher Copyright:
© 2017 American Chemical Society.
PY - 2017/10/4
Y1 - 2017/10/4
N2 - Nanoscale UiO-66 Zr6(OH)4O4(C6O4H4)6 has been synthesized with a series of carboxylic acid modulators, R-COOH (where R = H, CH3, CF3, and CHC12). The phase purity and size of each MOF was confirmed by powder X-ray diffraction, BET surface area analysis, and scanning transmission electron microscopy (STEM). Size control of UiO-66 crystals from 20 nm to over 1 μm was achieved, and confirmed by STEM. The colloidal stability of each MOF was evaluated by dynamic light scattering and was found to be highly dependent on the modulator conditions utilized in the synthesis, with both lower pKa and higher acid concentration resulting in more stable structures. Furthermore, STEM was carried out on both colloidally stable samples and those that exhibited a large degree of aggregation, which allowed for visualization of the different degrees of dispersion of the samples. The use of modulators at higher concentrations and with lower pKas leads to the formation of more defects, as a consequence of terephthalic acid ligands being replaced by modulator molecules, thereby enhancing the colloidal stability of the UiO-66 nanoparticles. These findings could have a significant impact on nanoscale MOF material syntheses and applications, especially in the areas of catalysis and drug delivery.
AB - Nanoscale UiO-66 Zr6(OH)4O4(C6O4H4)6 has been synthesized with a series of carboxylic acid modulators, R-COOH (where R = H, CH3, CF3, and CHC12). The phase purity and size of each MOF was confirmed by powder X-ray diffraction, BET surface area analysis, and scanning transmission electron microscopy (STEM). Size control of UiO-66 crystals from 20 nm to over 1 μm was achieved, and confirmed by STEM. The colloidal stability of each MOF was evaluated by dynamic light scattering and was found to be highly dependent on the modulator conditions utilized in the synthesis, with both lower pKa and higher acid concentration resulting in more stable structures. Furthermore, STEM was carried out on both colloidally stable samples and those that exhibited a large degree of aggregation, which allowed for visualization of the different degrees of dispersion of the samples. The use of modulators at higher concentrations and with lower pKas leads to the formation of more defects, as a consequence of terephthalic acid ligands being replaced by modulator molecules, thereby enhancing the colloidal stability of the UiO-66 nanoparticles. These findings could have a significant impact on nanoscale MOF material syntheses and applications, especially in the areas of catalysis and drug delivery.
KW - Colloidal stability
KW - Coordination modulation
KW - Metal-organic frameworks
KW - Nanoparticle
KW - Size control
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U2 - 10.1021/acsami.7b01040
DO - 10.1021/acsami.7b01040
M3 - Article
C2 - 28509530
AN - SCOPUS:85032985326
SN - 1944-8244
VL - 9
SP - 33413
EP - 33418
JO - ACS Applied Materials and Interfaces
JF - ACS Applied Materials and Interfaces
IS - 39
ER -