Department of Materials Science and Engineering, Northwestern University , 2220 Campus Drive, Evanston, Illinois 60208, United States.
Department of Chemistry, King Abdulaziz University , Jeddah 21589, Saudi Arabia.
ACS Appl Mater Interfaces. 2017 Oct 4;9(39):33413-33418. doi: 10.1021/acsami.7b01040. Epub 2017 May 16.
Nanoscale UiO-66 Zr(OH)O(COH) has been synthesized with a series of carboxylic acid modulators, R-COOH (where R = H, CH, CF, and CHCl). 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 pKs 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.
纳米级 UiO-66Zr(OH)O(COH) 已通过一系列羧酸调节剂 R-COOH（其中 R = H、CH、CF 和 CHCl）合成。粉末 X 射线衍射、BET 表面积分析和扫描透射电子显微镜（STEM）证实了每个 MOF 的相纯度和尺寸。成功实现了 UiO-66 晶体从 20nm 到 1μm 以上的尺寸控制，并通过 STEM 进行了确认。通过动态光散射评估了每个 MOF 的胶体稳定性，发现其高度依赖于合成中使用的调节剂条件，较低的 pKa 和较高的酸浓度会导致结构更加稳定。此外，还对胶体稳定的样品和表现出高度聚集的样品进行了 STEM 研究，这使得可以可视化样品的不同分散程度。使用更高浓度和更低 pKa 的调节剂会导致形成更多的缺陷，因为对苯二甲酸配体被调节剂分子取代，从而增强了 UiO-66 纳米粒子的胶体稳定性。这些发现可能对纳米级 MOF 材料的合成和应用产生重大影响，特别是在催化和药物输送领域。
