Photosynthetic System Based on a Polyoxometalate-Based Dehydrated Metal-Organic Framework for Nitrogen Fixation

Area of Science:

• Materials Science
• Catalysis
• Inorganic Chemistry

Background:

• Biological nitrogen fixation relies on nitrogenase's π-back-bonding mechanism, presenting challenges for artificial systems due to the N≡N bond's activation barrier.
• Developing efficient and reusable photocatalysts for artificial nitrogen fixation under mild conditions is crucial.

Purpose of the Study:

• To create an enzyme-mimicking photocatalyst for efficient artificial nitrogen fixation.
• To overcome the activation barrier of the N≡N bond using a novel composite material.

Main Methods:

• A charge-assisted self-assembly process was used to encapsulate polyoxometalate (POM) within dehydrated Zr-based metal-organic framework (d-UiO-66).
• The dehydration of d-UiO-66 facilitates nitrogen chemisorption and activation via unpaired d-orbital electrons.
• POM incorporation enhances charge separation for efficient electron transfer to N₂.

Main Results:

• The composite photocatalyst, SiW₉Fe₃@d-UiO-66, demonstrated significant nitrogen photofixation activity.
• Catalytic efficiency was enhanced 9.0 times compared to d-UiO-66 alone.
• An apparent quantum efficiency (AQE) of 0.254% at 550 nm was achieved.

Conclusions:

• The "working-in-tandem" strategy of POMs and d-UiO-66 is vital for enhancing artificial ammonia synthesis.
• This study presents a new paradigm for developing efficient artificial catalysts for nitrogen photofixation, mimicking biological processes.