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Conjugated Covalent Organic Frameworks via Michael Addition-Elimination
M Rajeswara Rao1, Yuan Fang1,2, Steven De Feyter2
1Department of Chemistry, McGill University , 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada.
Journal of the American Chemical Society
|January 17, 2017
Summary
Researchers developed new 2D π-conjugated covalent organic frameworks (COFs) using a novel Michael addition-elimination reaction. These materials exhibit tunable electronic properties and can detect explosives, expanding COF applications.
Area of Science:
- Materials Science
- Organic Chemistry
- Polymer Chemistry
Background:
- Dynamic covalent chemistry is crucial for creating complex materials like covalent organic frameworks (COFs).
- Current synthetic methods for π-conjugated COFs, primarily Schiff base condensation, are limited, yielding materials with moderate electron delocalization and susceptibility to hydrolysis.
- Existing imine-linked COFs have restricted properties and stability, hindering broader applications.
Purpose of the Study:
- To introduce a new dynamic polymerization method for synthesizing novel π-conjugated two-dimensional (2D) covalent organic frameworks (COFs).
- To explore the electronic and optical properties of these newly synthesized COFs.
- To demonstrate the potential of these COFs in sensing applications, specifically for explosives.
Main Methods:
- Utilized a Michael addition-elimination reaction between structurally diverse β-ketoenols and amines for polymerization.
- Synthesized crystalline powders and exfoliated micron-size sheets of the 2D π-conjugated COFs.
- Characterized the COFs' π-conjugation through reduced band gaps (1.8-2.2 eV), solid-state luminescence, and electrochemical doping.
Main Results:
- Successfully prepared novel 2D π-conjugated COFs via a new dynamic polymerization route.
- Observed significantly reduced band gaps, solid-state luminescence, and formation of midgap polaronic states upon electrochemical doping.
- Demonstrated protonation control over electron delocalization and direct sensing of triacetone triperoxide (TATP) via fluorescence quenching.
Conclusions:
- The new Michael addition-elimination reaction provides a versatile synthetic route to advanced π-conjugated COFs with tunable properties.
- These novel COFs exhibit enhanced electronic delocalization, luminescence, and electrochemical activity.
- The developed COFs show promise for sensitive detection of explosives like TATP and offer tunable electronic properties through protonation.
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