Surface-like NO_x Reduction at an Atomically-Precise Tricopper Cluster.

Area of Science:

• Catalysis
• Environmental Chemistry
• Materials Science

Background:

• Combustion and fertilizers increase environmental nitrogen oxides (NOx).
• Copper catalysts are promising for NOx remediation, but reaction mechanisms remain unclear.
• Understanding elementary steps is crucial for designing efficient catalysts.

Purpose of the Study:

• To prepare and characterize a novel copper cluster for NOx reduction.
• To elucidate the catalytic mechanism of nitrogen oxide conversion to nitrogen gas.
• To map the complete denitrification cycle at a molecular level.

Main Methods:

• Synthesis of a molecular tricuprous μ3-oxo complex.
• Preparation of a reduced, surface-like copper cluster.
• Characterization using spectroscopy and electronic structure calculations.
• Catalytic studies for NOx reductive coupling and reduction of nitrate/nitrite.

Main Results:

• A highly reactive, surface-like copper cluster (2) with σ-aromaticity was synthesized.
• Cluster 2 effectively catalyzes the reductive coupling of NO to N2, via N2O.
• Sequential oxygen atom transfer steps were identified as the key mechanism.
• Complete denitrification cycle was mapped, including stoichiometric reduction of NO3- and NO2-.

Conclusions:

• The novel copper cluster provides insights into NOx remediation mechanisms.
• σ-aromaticity in the copper core facilitates two-electron chemistry for denitrification.
• This atomically-precise cluster enables a comprehensive understanding of the catalytic cycle.