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Related Concept Videos

Aromatic Hydrocarbon Anions: Structural Overview01:18

Aromatic Hydrocarbon Anions: Structural Overview

3.9K
Neutral hydrocarbons like cyclopentadiene with an odd number of carbon atoms and one intervening CH2 group in the ring are not aromatic. Cyclopentadiene with 4 π electrons does not satisfy the 4n + 2 π electron rule. Additionally, the intervening CH2 group is sp3 hybridized and lacks a vacant p orbital, thereby interrupting the overlap of p orbitals in a continuous manner and preventing the delocalization of π electrons throughout the ring.
Due to the absence of continuous...
3.9K
Frost Circles for Different Conjugated Systems01:18

Frost Circles for Different Conjugated Systems

3.9K
The inscribed polygon method is consistent with Hückel’s 4n + 2 rule and helps to learn whether the given cyclic compound is aromatic or not. The compound is stable and aromatic if every bonding molecular orbital (MO) is completely filled with a pair of electrons. However, if the non-bonding or antibonding orbitals are filled with electrons, the compound is unstable and not aromatic. Consider the Frost circle diagrams for cycloalkenes containing 4 to 8 carbons.
3.9K
Five-Membered Heterocyclic Aromatic Compounds: Overview01:13

Five-Membered Heterocyclic Aromatic Compounds: Overview

5.8K
Heterocyclic aromatic compounds are cyclic compounds that are aromatic and have one or more heteroatoms—atoms other than carbon, in the ring. Depending upon the number of atoms present in the ring, they can be either five or six-membered. Examples of five-membered heterocyclic aromatic compounds include pyrrole, furan, thiophene, and imidazole. Pyrrole consists of one nitrogen atom having one lone pair of electrons. Furan and thiophene have one oxygen and one sulfur heteroatom,...
5.8K
Aromatic Hydrocarbon Cations: Structural Overview01:18

Aromatic Hydrocarbon Cations: Structural Overview

4.0K
Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
Removing one hydrogen from the intervening CH2 group...
4.0K
Conformations of Cyclohexane02:11

Conformations of Cyclohexane

16.0K
Cyclohexane does not exist in a planar form due to the high angle and torsional strain it would experience in the planar structure. Instead, it adopts non-planar chair and boat conformations.
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal...
16.0K
Criteria for Aromaticity and the Hückel 4n + 2 Rule01:20

Criteria for Aromaticity and the Hückel 4n + 2 Rule

13.9K
Like benzene, cyclobutadiene and cyclooctatetraene are cyclic compounds with alternate single and double bonds. However, their chemical behavior differs from benzene, as they are unstable and not aromatic. So, what are the structural characteristics of unsaturated compounds categorized as aromatic?  
For the first time, Eric Hückel, a German chemical physicist, derived a set of structural features for a compound to be classified as aromatic. This is now known as Hückel’s rule or the 4n +...
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Updated: Feb 17, 2026

Microfluidic-based Synthesis of Covalent Organic Frameworks COFs: A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface
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Microfluidic-based Synthesis of Covalent Organic Frameworks COFs: A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface

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Mesoporous 2D covalent organic frameworks based on shape-persistent arylene-ethynylene macrocycles.

Haishen Yang1, Ya Du1, Shun Wan2

  • 1Department of Chemistry and Biochemistry , University of Colorado Boulder , CO 80309 , USA .

Chemical Science
|December 9, 2017
PubMed
Summary
This summary is machine-generated.

This study introduces a macrocycle-to-framework strategy for creating covalent organic frameworks (COFs). This method utilizes shape-persistent macrocycles to build tunable, mesoporous 2D COFs with adjustable pore sizes.

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Area of Science:

  • Materials Science
  • Supramolecular Chemistry
  • Nanotechnology

Background:

  • Covalent Organic Frameworks (COFs) are crystalline porous polymers.
  • Designing COFs with controlled porosity and topology remains a challenge.
  • Macrocycles offer unique structural motifs for framework construction.

Purpose of the Study:

  • To explore a macrocycle-to-framework strategy for COF synthesis.
  • To construct well-ordered mesoporous 2D COFs using specific macrocycles.
  • To investigate the relationship between macrocycle structure and resulting COF properties.

Main Methods:

  • Synthesis of covalent organic frameworks (COFs) using a macrocycle-to-framework approach.
  • Utilizing tritopic arylene-ethynylene macrocycles as building blocks.
  • Characterization via Powder X-ray Diffraction (PXRD) and gas adsorption (NLDFT).

Main Results:

  • Successfully prepared mesoporous 2D COFs (AEM-COF-1 and AEM-COF-2).
  • Achieved fully eclipsed AA stacking with large accessible pore sizes (34-39 Å).
  • Demonstrated that larger macrocycles lead to expanded COF pore sizes.

Conclusions:

  • The macrocycle-to-framework strategy is effective for creating tunable COFs.
  • This approach allows for control over COF topology and porosity.
  • It offers a promising route to expand structural diversity and hierarchical pore structures in COFs.