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Related Concept Videos

Photochemical Electrocyclic Reactions: Stereochemistry01:26

Photochemical Electrocyclic Reactions: Stereochemistry

The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Thermal and Photochemical Electrocyclic Reactions: Overview01:26

Thermal and Photochemical Electrocyclic Reactions: Overview

Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
Cycloaddition Reactions: MO Requirements for Photochemical Activation01:12

Cycloaddition Reactions: MO Requirements for Photochemical Activation

Some cycloaddition reactions are activated by heat, while others are initiated by light. For example, a [2 + 2] cycloaddition between two ethylene molecules occurs only in the presence of light. It is photochemically allowed but thermally forbidden.
Aromatic Hydrocarbon Cations: Structural Overview01:18

Aromatic Hydrocarbon Cations: Structural Overview

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 with both...
Thermal Electrocyclic Reactions: Stereochemistry01:17

Thermal Electrocyclic Reactions: Stereochemistry

The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Aromatic Hydrocarbon Anions: Structural Overview01:18

Aromatic Hydrocarbon Anions: Structural Overview

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 overlap of p...

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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
08:42

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

Published on: July 10, 2017

Structural Engineering of Photoisomerizable Covalent Organic Frameworks: Design Principles and Functional

Guansheng Yang1, Fengqian Chen1, Qianrong Fang1

  • 1State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Changchun 130012, P. R. China.

Polymer Science & Technology (Washington, D.C.)
|June 8, 2026
PubMed
Summary
This summary is machine-generated.

Photoisomerizable covalent organic frameworks (COFs) offer advanced smart materials by overcoming limitations of conventional systems. This review details COF design, synthesis, and mechanisms for enhanced performance in applications like gas separation and remediation.

Keywords:
ApplicationsCovalent Organic FrameworksPhotoisomerizationSynthesis StrategiesTopological Structures

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Area of Science:

  • Materials Science
  • Chemistry
  • Nanotechnology

Background:

  • Photoisomerization enables light-triggered molecular transformations for smart materials.
  • Conventional photoisomeric systems suffer from poor kinetics, rigidity, and cyclability.
  • Covalent organic frameworks (COFs) offer tunable, stable platforms for integrating photoresponsive units.

Purpose of the Study:

  • To systematically review recent advances in photoisomerizable COFs.
  • To highlight design strategies, synthetic methods, and mechanistic insights.
  • To explore the potential of these materials in advanced applications.

Main Methods:

  • Review of rational design strategies for photoswitchable building blocks and COF geometries.
  • Examination of innovative synthetic methodologies for precise functionalization.
  • Analysis of mechanistic insights into light-driven transformations within COF nanopores.

Main Results:

  • Photoisomerizable COFs overcome limitations of conventional systems, offering improved performance.
  • Tailored design and synthesis enable precise control over photoresponsive behavior.
  • Understanding structure-property relationships guides the development of advanced functionalities.

Conclusions:

  • Photoisomerizable COFs represent a promising class of materials for smart applications.
  • Further research into design, synthesis, and mechanisms will enhance performance and durability.
  • These materials bridge the gap between fundamental science and real-world applications in areas like separation and catalysis.