Linker Torsional Angle Engineering in Metal-Organic Frameworks Enables Boosted O₂ Photoactivation for Organic...

Area of Science:

• Materials Science
• Photochemistry
• Organic Synthesis

Background:

• Controlling reactive oxygen species (ROSs) generation via O2 photoactivation is vital for organic synthesis but challenging.
• Metal-organic frameworks (MOFs) offer tunable platforms for photocatalysis.

Purpose of the Study:

• To demonstrate precise regulation of ROSs generation in MOFs by modulating linker torsional angles.
• To achieve efficient photocatalytic organic synthesis using tailored MOFs.

Main Methods:

• Construction of two MOFs, Ni-TTPz-α and Ni-TTPz-β, with isomeric linkers differing in planarity.
• Photocatalytic experiments under visible light to assess ROSs generation (superoxide radicals and singlet oxygen).
• Application of MOFs in the oxidative coupling of benzylamine.
• Computational studies to elucidate the mechanism of ROSs generation.

Main Results:

• Ni-TTPz-α, with a planar α-thiophene linker, significantly boosted superoxide radical (O2•−) production.
• Ni-TTPz-β, with a non-planar β-linker, predominantly generated singlet oxygen (1O2) with lower efficiency.
• Ni-TTPz-α achieved a 99% yield in benzylamine oxidative coupling, outperforming Ni-TTPz-β (48%).
• An 'angle-induced restricted twist effect' in planar linkers facilitates electron transfer for O2•− generation.

Conclusions:

• Modulating linker torsional angles in MOFs is a viable strategy for precise ROSs generation control.
• Ni-TTPz-α demonstrates high efficiency in visible-light-driven O2•− production for organic synthesis.
• The study provides mechanistic insights into MOF-based photocatalysis via electron transfer pathways.