Related Experiment Video
Updated: Jun 28, 2026
07:36
Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy
Published on: November 9, 2019
Pre-Crosslinked Network-Mediated Dual Exchange Enables Boosting Chiroptical Activity and Decoupled Two-Level
Xinlin Zha1, Mengjuan Zuo1, Zhenzhen Jiang1
1Key Laboratory of Textile Fiber and Products, Ministry of Education, Wuhan Textile University, Wuhan, China.
Angewandte Chemie (International Ed. in English)
|June 26, 2026
Summary
Researchers developed a new method to create crystalline covalent organic frameworks (COFs) with enhanced chirality. This strategy amplifies chiroptical activity and allows for multilevel chirality control in advanced materials.
Area of Science:
- Materials Science
- Organic Chemistry
- Nanotechnology
Background:
- Crystalline covalent organic frameworks (COFs) are difficult to synthesize with strong chiroptical properties.
- Rapid crystallization hinders effective chirality induction in conventional COF synthesis.
Purpose of the Study:
- To develop a strategy for amplified chiroptical activity and decoupled multilevel chirality in COFs.
- To overcome limitations in chirality induction during COF crystallization.
Main Methods:
- A pre-crosslinked network-mediated dual-exchange strategy was employed.
- Monomers were immobilized in an amorphous imine network to control crystallization kinetics.
- Concurrent amine and aldehyde exchange processes were utilized to prolong the chirality induction window.
Main Results:
- The synthesized COFs exhibited significantly enhanced chiroptical activity with dissymmetry factors (|gabs|) up to 0.071.
- A tenfold increase in chiroptical response was observed compared to conventional methods.
- Supramolecular transcription enabled the decoupling of mesoscopic helicity and molecular chirality within the framework.
Conclusions:
- The dual-exchange strategy effectively amplifies chiroptical activity in COFs.
- Independent control over molecular and mesoscopic chirality is achievable.
- This approach offers a general method for programming multilevel chirality in crystalline frameworks.
Related Concept Videos
01:26Photochemical 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
Selection Rules: Photochemical Activation
02:25Molecules with Multiple Chiral Centers
Molecules that possess multiple chiral centers can afford a large number of stereoisomers. For instance, while some molecules like 2-butanol have one chiral center, defined as a tetrahedral carbon atom with four different substituents attached, several molecules like butane-2,3-diol have multiple chiral centers. A simple formula to predict the number of stereoisomers possible for a molecule with n chiral centers is 2n. However, there can be a lower number where some of the stereoisomers are...
01:16Cycloaddition Reactions: MO Requirements for Thermal Activation
Thermal cycloadditions are reactions where the source of activation energy needed to initiate the reaction is provided in the form of heat. A typical example of a thermally-allowed cycloaddition is the Diels–Alder reaction, which is a [4 + 2] cycloaddition. In contrast, a [2 + 2] cycloaddition is thermally forbidden.
01:17Thermal 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.
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.
01:04Crossed Aldol Reactions: Overview
Crossed aldol addition is the reaction between two different carbonyl compounds under acidic or basic conditions. Here, both the carbonyl compounds function as nucleophiles and electrophiles. As shown in Figure 1, such a reaction yields a mixture of products, two of which are formed via self-condensation, while the remaining two are formed via crossed-condensation. Without adjustment, the reaction's usefulness in organic chemistry is decreased.
01:18β-Dicarbonyl Compounds via Crossed Claisen Condensations
Crossed Claisen condensations are base-promoted reactions between two different ester molecules producing β-dicarbonyl compounds. The reaction involving esters, with both containing α hydrogen, results in a mixture of four different products that are difficult to isolate. This reduces the synthetic utility of the reaction.