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Title: Role of Modulators in Controlling the Colloidal Stability and Polydispersity of the UiO-66 Metal–Organic Framework

Abstract

Nanoscale UiO-66 Zr6(OH)4O4(C8O4H4)6 has been synthesized with a series of carboxylic acid modulators, R-COOH (where R = H, CH3, CF3, and CHCl2). 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.

Authors:
; ; ;  [1]; ORCiD logo; ORCiD logo [2]; ORCiD logo [1]
  1. Department of Materials Science and Engineering, Northwestern University, 2220 Campus Drive, Evanston, Illinois 60208, United States
  2. Department of Chemistry, King Abdulaziz University, Jeddah 21589, Saudi Arabia
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
U.S. AIR FORCE- OFFICE OF SCIENTIFIC RESEARCH
OSTI Identifier:
1418044
Resource Type:
Journal Article
Resource Relation:
Journal Name: ACS Applied Materials and Interfaces; Journal Volume: 9; Journal Issue: 39
Country of Publication:
United States
Language:
ENGLISH
Subject:
36 MATERIALS SCIENCE

Citation Formats

Morris, William, Wang, Shunzhi, Cho, David, Auyeung, Evelyn, Li, Peng, Farha, Omar K., and Mirkin, Chad A.. Role of Modulators in Controlling the Colloidal Stability and Polydispersity of the UiO-66 Metal–Organic Framework. United States: N. p., 2017. Web. doi:10.1021/acsami.7b01040.
Morris, William, Wang, Shunzhi, Cho, David, Auyeung, Evelyn, Li, Peng, Farha, Omar K., & Mirkin, Chad A.. Role of Modulators in Controlling the Colloidal Stability and Polydispersity of the UiO-66 Metal–Organic Framework. United States. doi:10.1021/acsami.7b01040.
Morris, William, Wang, Shunzhi, Cho, David, Auyeung, Evelyn, Li, Peng, Farha, Omar K., and Mirkin, Chad A.. Fri . "Role of Modulators in Controlling the Colloidal Stability and Polydispersity of the UiO-66 Metal–Organic Framework". United States. doi:10.1021/acsami.7b01040.
@article{osti_1418044,
title = {Role of Modulators in Controlling the Colloidal Stability and Polydispersity of the UiO-66 Metal–Organic Framework},
author = {Morris, William and Wang, Shunzhi and Cho, David and Auyeung, Evelyn and Li, Peng and Farha, Omar K. and Mirkin, Chad A.},
abstractNote = {Nanoscale UiO-66 Zr6(OH)4O4(C8O4H4)6 has been synthesized with a series of carboxylic acid modulators, R-COOH (where R = H, CH3, CF3, and CHCl2). 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.},
doi = {10.1021/acsami.7b01040},
journal = {ACS Applied Materials and Interfaces},
number = 39,
volume = 9,
place = {United States},
year = {Fri Apr 07 00:00:00 EDT 2017},
month = {Fri Apr 07 00:00:00 EDT 2017}
}
  • Metal–organic frameworks (MOFs) containing Mo Schiff base complexes were prepared by post-synthesis method and applied as efficient catalysts in the epoxidation of alkenes with tert-BuOOH. In this manner, UiO-66-NH{sub 2} (UiO=University of Oslo) MOF was reacted with salicylaldehyde and thiophene-2-carbaldehyde to produce bidentate Schiff bases. Then, the Schiff base ligands were used for immobilization of molybdenyl acetylacetonate. These new catalysts were characterized by FT-IR, UV–vis spectroscopic techniques, X-ray diffraction (XRD), BET, inductively coupled plasma atomic emission spectroscopy (ICP-AES) and field emission scanning electron microscopy (FE-SEM). These catalytic systems showed excellent activity in the epoxidation of alkenes such as cyclic andmore » linear ones with tert-butyl hydroperoxide (TBHP) in 1,2-dichloroethane, and reused several times without any appreciable loss of their activity. - Graphical abstract: Efficient alkene epoxidation with TBHP catalyzed by heterogeneous and reusable molybdenum base catalysts is reported. - Highlights: • UiO-66-NH{sub 2} was modified with salicylaldehyde and thiophene-2-carbaldehyde. • The Schiff base groups were used for immobilization of MoO{sub 2}(acac){sub 2}. • The heterogeneous catalysts were prepared. • The prepared catalysts were used for epoxidation of alkenes. • Compared to other catalyst, our catalysts were more efficient and forceful.« less
  • The ability to encapsulate photo-active guest molecules within the pores of metal organic frameworks (MOFs) affords the opportunity to develop robust photocatalysts as well as solar energy conversion systems. An important criteria for such systems is stability of the new materials towards moisture, high temperatures, etc which preclude the use of many MOF frameworks. Here, the ability to encapsulate [Ru(II)(2,2′-bipyridine){sub 3}]{sup 2+}([Ru(bpy){sub 3}]{sup 2+}) into the cavities of the zirconium based MOF Uio-66 as well as the photophysical properties of the complex are reported. The X-ray powder diffraction data of the orange Uio-66 powder are consistent with the formation ofmore » Uio-66 in the presence of [Ru(bpy){sub 3}]{sup 2+}. The steady state emission exhibits a significant bathochromic shift from 603 nm in ethanol to 610 nm in Uio-66. The corresponding emission decay of the encapsulated [Ru(bpy){sub 3}]{sup 2+} complex is biexponential with a fast component of 128 ns and a slower component of 1176 ns (20 deg C). The slow component is consistent with encapsulation of [Ru(bpy){sub 3}]{sup 2+} into cavities with restricted volume that prevents the population of a triplet ligand field transition that is anti-bonding with respect to the Ru-N bonds. The origin of the fast component is unclear but may involve interactions of the [Ru(bpy){sub 3}]{sup 2+} encapsulated within large cavities formed through missing ligand defect sites within the Uio-66 materials. Co-encapsulated quenchers contained within these larger cavities gives rise to the reduced lifetimes of the [Ru(bpy){sub 3}]{sup 2+} complexes. - Graphical abstract: One-pot synthesis of Ru(II)tris(2,2-bipyridine)@Uio-66 (left) and the effects of encapsulation on the excited state energy levels and decay pathways of the Ru(II)tris(2,2-bipyridine) complex (right).« less