Photosystem II-Inspired Ce-MOF for Selectively Coupling Photocatalytic Nitro-to-Azoxy Conversion with Water...

Area of Science:

• Materials Science
• Photocatalysis
• Green Chemistry

Background:

• Integrating photocatalytic water oxidation with organic transformations is hindered by poor charge separation and intermediate control.
• Photosystem II (PSII) offers a model with spatially separated redox centers for efficient catalysis.

Purpose of the Study:

• To design a metal-organic framework (MOF) mimicking PSII's architecture for coupled water oxidation and organic synthesis.
• To achieve efficient visible-light-driven conversion of nitrobenzene to azoxybenzene with simultaneous water oxidation.

Main Methods:

• Synthesis and characterization of a cerium(IV)-based MOF (Ce(IV)-DPA) using anthracene-derived ligands.
• Single-crystal X-ray diffraction to determine crystal structure and substrate coordination.
• Density Functional Theory (DFT) calculations to elucidate electronic structure and electron transfer pathways.
• Isotopic tracer studies to confirm the proton source in the reaction mechanism.

Main Results:

• Ce(IV)-DPA demonstrated efficient visible-light-induced nitrobenzene to azoxybenzene conversion (91% yield, 96% selectivity) coupled with water oxidation.
• Atomic-resolution evidence of nitrobenzene coordination to Ce(IV) centers was obtained, guiding electron transfer.
• The MOF structure facilitated sequential proton-coupled electron transfers (PCET), mirroring PSII.
• Ce(IV)-DPA outperformed Ce(III)-DPA analogs by 49% in yield and showed high stability over six cycles.

Conclusions:

• The Ce(IV)-DPA framework effectively mimics PSII's compartmentalized redox centers, enabling synergistic photocatalysis.
• This MOF provides a new catalytic paradigm for scalable solar-to-chemical conversion, producing high-value nitrogen chemicals.
• The study offers insights into substrate activation and intermediate regulation in MOF-based photocatalysis.