在Cr3中具有高度选择性和可逆性的O2结合 ((1,3,5-二甲酸) 2
Leslie J Murray1, Mircea Dinca, Junko Yano
1Department of Chemistry, University of California, Berkeley, California 94720, USA.
Journal of the American Chemical Society
|May 21, 2010
概括
本研究介绍了一种基于的新型金属有机框架,Cr(3)(BTC)(2),用于选择性吸附氧气. 这种材料具有异常的O(2) /N(2) 选择性,对于气体分离应用至关重要.
科学领域:
- 材料科学 材料科学 材料科学
- 无机化学 无机化学 有机化学
- 纳米技术纳米技术
背景情况:
- 金属有机框架 (MOF) 是具有可调节性质的多孔材料.
- 选择性气体吸附对于气体分离和储存等应用至关重要.
- 基于的MOF具有独特的电子和结构特性.
研究的目的:
- 为了合成和表征一种基于的新型金属有机框架,Cr(3)(BTC)(2).
- 为了研究Cr的气体吸附特性,特别是氧和.
- 探索Cr(3)(BTC)(2) 在选择性氧气捕获方面的潜力.
主要方法:
- 在DMF中,通过Cr (CO) 的反应与三酸合成Cr (Cr) 3 (BTC) 2 (BTC).
- 通过将DMF换成甲醇和真空加热来溶解框架.
- 气体吸附测量 (N(2) 在77K,O(2) 和N(2) 在298K).
- 光谱分析 (红外线,X射线吸收) 和中子粉光散.
主要成果:
- 合成的材料Cr3BTC2与Cu3BTC2具有同结构,表面积很大 (1810米2/gBET).
- 在298K时,Cr(3) (((BTC) ((2) 具有显著的O(2) /N(2) 选择性因子,在298K时为22,在低压下具有高O(2) 吸收率 (11重量%) .
- 光谱和衍射数据证实O2通过部分电荷转移到Cr2中心结合,改变Cr-Cr距离.
结论:
- (Cr) 是选择性氧气捕获和分离的一个有前途的材料.
- 2结合的机制涉及与暴露的Cr2中心的相互作用.
- 该框架展示了可逆的O2吸附/脱附在多个循环中.
相关概念视频
Reactions at the Benzylic Position: Oxidation and Reduction
The benzylic position describes the position of a carbon atom attached directly to a benzene ring. Benzene by itself does not undergo oxidation. In contrast, the benzylic carbon is quite reactive in the presence of strong oxidizing agents such as KMnO4 or H2CrO4. Therefore, alkylbenzenes are readily oxidized to benzoic acid, irrespective of the type of alkyl groups.
Woodward–Hoffmann Selection Rules and Microscopic Reversibility
Electrocyclic reactions, cycloadditions, and sigmatropic rearrangements are concerted pericyclic reactions that proceed via a cyclic transition state. These reactions are stereospecific and regioselective. The stereochemistry of the products depends on the symmetry characteristics of the interacting orbitals and the reaction conditions. Accordingly, pericyclic reactions are classified as either symmetry-allowed or symmetry-forbidden. Woodward and Hoffmann presented the selection criteria for...
Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
The rate of acid-catalyzed hydration of alkenes depends on the alkene's structure, as the presence of alkyl substituents at the double bond can significantly influence the rate.
meta-Directing Deactivators: –NO2, –CN, –CHO, –⁠CO2R, –COR, –CO2H
All meta-directing substituents are deactivating groups. These substituents withdraw electrons from the aromatic ring, making the ring less reactive toward electrophilic substitution. For example, the nitration of nitrobenzene is 100,000 times slower than that of benzene because of the deactivating effect of the nitro group. The first step in an electrophilic aromatic substitution is the addition of an electrophile to form a resonance-stabilized carbocation. The energy diagrams for the...
Regioselectivity and Stereochemistry of Hydroboration
A significant aspect of hydroboration–oxidation is the regio- and stereochemical outcome of the reaction.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH3
All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...


