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Covalent Bonds

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Covalent Bonds

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When two atoms share electrons to complete their valence shells, they create a covalent bond. An atom's electronegativity—the force with which shared electrons are pulled towards an atom—determines how the electrons are shared. Molecules formed with covalent bonds can be either polar or nonpolar. Atoms with similar electronegativities form nonpolar covalent bonds; the electrons are shared equally. Atoms with different electronegativities share electrons unequally,...

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Proteins can undergo many types of post-translational modifications, often in response to changes in their environment. These modifications play an important role in the function and stability of these proteins. Covalently linked molecules include functional groups, such as methyl, acetyl, and phosphate groups, and also small proteins, such as ubiquitin. There are around 200 different types of covalent regulators that have been identified.
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Updated: Feb 12, 2026

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

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

3D Anionic Silicate Covalent Organic Framework with srs Topology.

Oussama Yahiaoui¹, Andrew N Fitch², Frank Hoffmann³

¹Department of Chemistry , Technische Universität Berlin , BA2, Hardenbergstraße 40 , 10623 Berlin , Germany.

Journal of the American Chemical Society

|April 5, 2018

Summary

Researchers synthesized a novel anionic 3D covalent organic framework (COF) using hypercoordinate silicon nodes. This new material, SiCOF-5, adopts a unique srs net topology, expanding the possibilities for advanced porous materials.

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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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Area of Science:

Materials Chemistry
Supramolecular Chemistry
Nanotechnology

Background:

Synthesizing 3D covalent organic frameworks (COFs) with novel topologies is difficult.
Existing 3D COFs are limited to tetrahedral building blocks.

Purpose of the Study:

To demonstrate the targeted synthesis of an anionic 3D COF with a three-coordinated srs net.
To expand the geometric diversity of COF structures.

Main Methods:

Utilized a new linkage for anionic silicate COFs based on hypercoordinate silicon nodes.
Reticulated dianionic hexacoordinate [SiO6]2- nodes with triphenylene building blocks.
Controlled nucleation and growth rates via gradual silicon source generation.

Main Results:

Successfully synthesized SiCOF-5, an anionic 3D COF.
SiCOF-5 crystallizes in a two-fold interpenetrated srs-c net.
The framework has the composition Na2[Si(C18H6O6)].

Conclusions:

Achieved targeted synthesis of a novel anionic 3D COF with an srs net topology.
Demonstrated the utility of hypercoordinate silicon nodes in COF construction.
Highlighted the importance of controlled reaction kinetics for successful crystallization.