A Metal-Organic Framework Platform Enabling Visible-to-Ultraviolet Upconversion-Driven Heterogeneous Photochemistry

Area of Science:

• Materials Science
• Photochemistry
• Nanotechnology

Background:

• Triplet-triplet annihilation photon upconversion (TTA-UC) converts low-energy photons to higher-energy photons, crucial for applications like photocatalysis and optoelectronics.
• Efficient and stable visible-to-ultraviolet (vis-to-UV) TTA-UC in solid materials is challenging due to issues like annihilator aggregation and poor photostability.
• Metal-organic frameworks (MOFs) offer tunable, stable platforms for integrating functional components.

Purpose of the Study:

• To develop a novel, stable material for efficient vis-to-UV TTA-UC.
• To investigate the utility of MOF-based TTA-UC systems in heterogeneous photochemical reactions.
• To establish a sustainable, mercury- and UV-lamp-free UV light source.

Main Methods:

• Co-incorporation of a p-terphenyl dicarboxylic acid annihilator (TP-(COOH)2) and an iridium sensitizer (Ir-(dFppy-COOH)3) into a Zr-based UiO-68 framework.
• Characterization of the hybrid MOF's structure, photophysical properties, and stability.
• Demonstration of the MOF's performance in vis-to-UV TTA-UC and application in uncaging MNI-caged l-glutamate.

Main Results:

• The hybrid MOF exhibits efficient vis-to-UV TTA-UC with a 0.60% upconversion efficiency upon 445 nm excitation.
• The rigid MOF structure effectively prevents chromophore aggregation, leading to excellent photostability.
• The MOF-based system successfully enabled spatiotemporally controlled uncaging in a heterogeneous photochemical reaction.

Conclusions:

• A stable, MOF-based platform for vis-to-UV TTA-UC in suspension has been successfully established.
• This MOF system demonstrates significant potential for sustainable photochemistry, photocatalysis, and advanced light-driven functional materials.
• The findings open new avenues for designing advanced upconversion materials within robust frameworks.