Wavelength-Selective Photochromism in a Naphthalenediimide-Based Metal-Organic Framework: Mechanism, Ultrafast...

Area of Science:

• Materials Science
• Chemistry
• Nanotechnology

Background:

• Metal-organic frameworks (MOFs) are porous materials with diverse applications.
• Naphthalenediimide (NDI) ligands are known for their electronic and optical properties.
• Photochromic materials change color upon light exposure, offering potential for optical switching and data storage.

Purpose of the Study:

• To synthesize and characterize a novel Zn(II)-based MOF incorporating NDI ligands.
• To investigate the ultrafast and reversible photochromic properties of the synthesized MOF.
• To explore the potential applications of this photoresponsive MOF in anticounterfeiting technologies.

Main Methods:

• Synthesis of a Zn(II)-based MOF with NDI ligands.
• Spectroscopic and structural analyses to elucidate photochromic mechanisms.
• Wavelength-dependent optical switching and fluorescence modulation studies.
• Application testing in inkless printing and fingerprint encryption.

Main Results:

• The novel MOF (1) exhibits ultrafast and reversible photochromism upon blue-violet light irradiation (395-465 nm).
• Photochromism is attributed to photoinduced electron transfer facilitated by hydrogen bonding and lone pair-π interactions, forming NDI radical anions.
• The MOF demonstrates significant photomodulated fluorescence quenching (∼80%) under visible light, enabling dual-mode optical switching.
• Successful application in anticounterfeiting technologies with high-contrast patterns and spatially controllable fluorescence.

Conclusions:

• The developed MOF possesses exceptional light sensitivity and rapid photochromic response.
• The material's dual-mode optical switching capability and wavelength-dependent responsiveness are key features.
• This NDI-based MOF shows significant promise as a multifunctional photoresponsive material for advanced optoelectronic and security applications.