Efficient room-temperature phosphorescence of covalent organic frameworks through covalent halogen doping

Area of Science:

• Materials Science
• Organic Chemistry
• Optoelectronics

Background:

• Organic room-temperature phosphorescence is a rare, spin-forbidden process with applications in optoelectronics and sensing.
• Covalent organic frameworks (COFs) offer unique structural benefits for designing phosphorescent materials but remain largely unexplored for this purpose.

Purpose of the Study:

• To develop highly phosphorescent covalent organic frameworks (COFs) through a novel covalent doping strategy.
• To explore the potential of these phosphorescent COFs in applications such as oxygen sensing.

Main Methods:

• Synthesized COFs via copolymerization of halogenated and unsubstituted phenyldiboronic acids.
• Employed covalent doping to control the distribution and concentration of functionalized units within the COF structure.
• Characterized the phosphorescence properties and oxygen sensing capabilities of the resulting materials.

Main Results:

• Achieved highly phosphorescent COFs with a high phosphorescence quantum yield (Φ_Phos ≤ 29%) at room temperature.
• Demonstrated that covalent halogen doping enhances intersystem crossing and minimizes triplet-triplet annihilation.
• Developed an efficient COF-based oxygen sensor utilizing the material's porosity and dual emission channels, with a wide dynamic detection range.

Conclusions:

• Covalent doping is an effective strategy for creating highly phosphorescent COFs.
• The developed phosphorescent COFs show promise for advanced applications, particularly in highly sensitive oxygen detection.