Related Experiment Video
Updated: Jun 12, 2026
07:36
Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy
Published on: November 9, 2019
Highly-selective and reversible O2 binding in Cr3(1,3,5-benzenetricarboxylate)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
Summary
This study introduces a novel chromium-based metal-organic framework, Cr(3)(BTC)(2), for selective oxygen adsorption. This material exhibits exceptional O(2)/N(2) selectivity, crucial for gas separation applications.
Area of Science:
- Materials Science
- Inorganic Chemistry
- Nanotechnology
Background:
- Metal-organic frameworks (MOFs) are porous materials with tunable properties.
- Selective gas adsorption is critical for applications like gas separation and storage.
- Chromium-based MOFs offer unique electronic and structural characteristics.
Purpose of the Study:
- To synthesize and characterize a novel chromium-based metal-organic framework, Cr(3)(BTC)(2).
- To investigate the gas adsorption properties of Cr(3)(BTC)(2), particularly for oxygen and nitrogen.
- To explore the potential of Cr(3)(BTC)(2) for selective oxygen capture.
Main Methods:
- Synthesis of Cr(3)(BTC)(2) via reaction of Cr(CO)(6) with trimesic acid in DMF.
- Desolvation of the framework by exchanging DMF for methanol and heating under vacuum.
- Gas adsorption measurements (N(2) at 77 K, O(2) and N(2) at 298 K).
- Spectroscopic analysis (Infrared, X-ray absorption) and neutron powder diffraction.
Main Results:
- The synthesized material, Cr(3)(BTC)(2), is isostructural to Cu(3)(BTC)(2) and possesses high surface area (1810 m(2)/g BET).
- Cr(3)(BTC)(2) exhibits a remarkable O(2)/N(2) selectivity factor of 22 at 298 K, with high O(2) uptake (11 wt%) at low pressure.
- Spectroscopic and diffraction data confirm O(2) binding via partial charge transfer to Cr(II) centers, altering Cr-Cr distances.
Conclusions:
- Cr(3)(BTC)(2) is a promising material for selective oxygen capture and separation.
- The mechanism of O(2) binding involves interaction with exposed Cr(II) centers.
- The framework demonstrates reversible O(2) adsorption/desorption over multiple cycles.
Related Concept Videos
00:59Reactions 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.
01:34Woodward–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...
02:34Regioselectivity 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.
01:13meta-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...
02:36Regioselectivity 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.
01:11ortho–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...