Department of Chemistry, The City College of New York, 160 Convent Ave, New York, New York 10031, United States.
Langmuir. 2013 Jan 8;29(1):168-74. doi: 10.1021/la302869m. Epub 2012 Dec 18.
Zirconium-based metal organic framework (Zr-MOF), UiO-66 and UiO-67, were synthesized and used as adsorbents of NO(2) at ambient temperatures in either dry or moist conditions. The samples were characterized before and after exposure to NO(2) by X-ray diffraction, scanning electron microscopy, N(2)-adsorption at 77 K, thermal analysis, and infrared spectroscopy. The results indicate the important effect of a ligand size on the adsorption of NO(2) on Zr-MOF materials. While the large size of the 4,4-benzenebiphenyldicarboxylic acid (BDPC) ligand has a positive impact on the adsorption of NO(2) on UiO-67 in moist conditions, the opposite effect is found in dry conditions. The large pore volume of UiO-67 enhances the adsorption of moisture and formation of nitric and nitrous acids. The small pore sizes of UiO-66 favor the NO(2) removal in dry conditions via dispersive forces. Upon interaction of NO(2) molecules with the Zr-MOF in dry conditions, the bond between the organic linker and metallic oxide center is broken, leading to the formation of nitrate and nitrite species. Moreover, organic ligands also contribute to the NO(2) reactive adsorption via nitration reaction.
锆基金属有机骨架（Zr-MOF）UiO-66 和 UiO-67 被合成并用作在干燥或潮湿条件下环境温度下吸附 NO(2)的吸附剂。在暴露于 NO(2)前后，通过 X 射线衍射、扫描电子显微镜、77 K 下的 N(2)吸附、热分析和红外光谱对样品进行了表征。结果表明，配体尺寸对 Zr-MOF 材料吸附 NO(2)的重要影响。虽然 4,4-联苯二甲酸（BDPC）配体的大尺寸对 UiO-67 在潮湿条件下吸附 NO(2)有积极影响，但在干燥条件下则相反。UiO-67 的大孔体积增强了水分的吸附和硝酸及亚硝酸的形成。UiO-66 的小孔径有利于通过分散力在干燥条件下去除 NO(2)。在干燥条件下，NO(2)分子与 Zr-MOF 相互作用时，有机配体与金属氧化物中心之间的键被打破，导致硝酸盐和亚硝酸盐物种的形成。此外，有机配体还通过硝化反应有助于 NO(2)的反应性吸附。
