Mechanically Interlocked Double-Walled Covalent Organic Framework with Cucurbit[8]Uril-Stabilized Viologen Radical...

Area of Science:

• Materials Chemistry
• Supramolecular Chemistry
• Organic Electronics

Background:

• Stabilizing organic radicals in crystalline frameworks is crucial for optoelectronics and sensing.
• Integrating functional radicals into covalent organic frameworks (COFs) presents significant challenges.

Purpose of the Study:

• To design and synthesize a radical-rich polyrotaxanated COF with enhanced radical stability and functionality.
• To explore the potential of macrocycle-assisted encapsulation for radical integration in COFs.

Main Methods:

• Synthesis of a polyrotaxanated covalent organic framework (VCB COF) using viologen radicals and cucurbit[8]uril (CB[8]) macrocycles.
• Electron paramagnetic resonance (EPR) spectroscopy for radical stability assessment.
• Photophysical and photoelectrochemical measurements.
• Molecular dynamics simulations and solid-state NMR.

Main Results:

• The VCB COF exhibited enhanced radical stability, retaining over 72% radical signal after 7 days in air.
• A 3-fold increase in photoluminescence intensity was observed.
• Stable photocurrent density of 1.3 μA cm⁻² with reversible switching was achieved.
• The double-walled architecture was confirmed through simulations and NMR.

Conclusions:

• Macrocycle-assisted encapsulation and mechanical bonding provide a generalizable strategy for integrating persistent radicals into COFs.
• The developed VCB COF demonstrates robust photoactive, redox-active, and spin-functional properties.
• This approach opens new avenues for designing advanced functional materials.