A Facile, Efficient, and General Synthetic Method to Amide-Linked Covalent Organic Frameworks
Zhi-Bei Zhou1, Xiang-Hao Han1, Qiao-Yan Qi1
1Key Laboratory of Synthetic and Self-Assembly Chemistry for Organic Functional Molecules, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China.
Journal of the American Chemical Society
|January 17, 2022
Summary
Researchers developed a new method to synthesize stable amide covalent organic frameworks (amide COFs). This efficient process converts readily available imine COFs into amide COFs, improving material accessibility for applications.
Area of Science:
- Materials Science
- Organic Chemistry
- Nanotechnology
Background:
- Amide-linked covalent organic frameworks (amide COFs) offer high stability and desirable polyamide structures for various applications.
- A significant limitation of amide COFs is their restricted accessibility, hindering widespread practical use.
- Existing synthesis methods for amide COFs are often complex or inefficient.
Purpose of the Study:
- To develop a facile, efficient, and scalable method for synthesizing crystalline amide COFs.
- To overcome the accessibility limitations of amide COFs by utilizing a novel linkage conversion strategy.
- To establish a foundation for exploring the practical applications of amide COFs.
Main Methods:
- A new linkage conversion strategy involving the oxidation of imine linkages in imine-linked COFs.
- Utilized potassium peroxymonosulfate (KHSO5) as a mild oxidant under ambient conditions.
- Demonstrated the method's generality and scalability through the synthesis of seven different imine-linked COFs and gram-scale production.
Main Results:
- Successfully synthesized crystalline amide COFs through the mild oxidation of imine-linked precursors.
- The conversion process was rapid, efficient, and completed under very mild reaction conditions.
- The developed method proved to be general, scalable, and applicable to a range of imine-linked COFs.
Conclusions:
- A novel and highly efficient method for synthesizing amide COFs from readily available imine-linked COFs has been established.
- This approach significantly enhances the accessibility of amide COFs, paving the way for their practical implementation.
- The developed synthetic strategy provides a robust platform for the future exploration and utilization of polyamide-based covalent organic frameworks.
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Amides are synthesized by treating carboxylic acids with amines in the presence of dehydrating agents like dicyclohexylcarbodiimide (DCC).
The DCC-promoted synthesis of amides begins with the protonation of DCC by carboxylic acid. The protonation makes it a better acceptor. Next, the addition of carboxylate to the protonated carbodiimide gives a reactive acylating agent.
Subsequently, the amine acts as a nucleophile that attacks the acylating agent to form a tetrahedral intermediate. In the...
The DCC-promoted synthesis of amides begins with the protonation of DCC by carboxylic acid. The protonation makes it a better acceptor. Next, the addition of carboxylate to the protonated carbodiimide gives a reactive acylating agent.
Subsequently, the amine acts as a nucleophile that attacks the acylating agent to form a tetrahedral intermediate. In the...
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01:28Structures of Carboxylic Acid Derivatives
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Structure of Carboxylic Acid Derivatives
Carboxylic acid derivatives contain an acyl group attached to a heteroatom such as chlorine, oxygen, or nitrogen. The carbonyl carbon and oxygen are both sp2-hybridized with an unhybridized p orbital.
The three sp2 orbitals of the carbonyl carbon form three σ bonds, one each with the carbonyl oxygen, the α carbon, and the heteroatom, whereas the other two sp2 orbitals of the carbonyl oxygen are occupied by the lone pairs. Further, the...
Carboxylic acid derivatives contain an acyl group attached to a heteroatom such as chlorine, oxygen, or nitrogen. The carbonyl carbon and oxygen are both sp2-hybridized with an unhybridized p orbital.
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01:19Amines to Amides: Acylation of Amines
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Various carboxylic acid derivatives (such as acid chlorides, esters, and anhydrides) can be used for the acylation of amines to yield amides. The reaction requires two equivalents of amines. The first amine molecule functions as a nucleophile and attacks the carbonyl carbon to produce a tetrahedral intermediate. This is followed by the loss of the leaving group and restoration of the C=O bond.
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01:11Nomenclature of Carboxylic Acid Derivatives: Amides and Nitriles
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Naming Amides
The IUPAC and common names of amides are derived from the parent carboxylic acid, by replacing the suffix “oic acid” and “ic acid,” respectively, with “amide.” In the following example, the IUPAC name ethanamide is derived from ethanoic acid, and the common name, acetamide, is obtained from acetic acid.
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01:28Preparation of 1° Amines: Gabriel Synthesis
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Strong bases like NaOH or KOH deprotonate the phthalimide to form the corresponding anion, which acts as a nucleophile. Further, the anion attacks an...
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