C-C bond coupling with sp³ C-H bond via active intermediates from CO₂ hydrogenation

Area of Science:

• Catalysis
• Green Chemistry
• Materials Science

Background:

• Methanol-mediated side-chain alkylation exhibits sluggish kinetics.
• CO2 hydrogenation presents a sustainable but challenging alternative for alkylation.

Purpose of the Study:

• To develop a novel catalytic system for side-chain alkylation using CO2 hydrogenation.
• To investigate the efficiency and mechanism of CO2 as an alkylation agent.

Main Methods:

• Utilized a binary metal oxide-zeolite tandem catalyst (Zn40Zr60O/CsX).
• Employed in-situ DRIFTS and DFT calculations to study reaction intermediates.

Main Results:

• Achieved 19.6% 4-methylpyridine (MEPY) conversion and 82% 4-ethylpyridine (ETPY) selectivity.
• The CO2 hydrogenation route demonstrated 6.5 times higher activity than methanol.
• Identified CHxO* species as the key intermediate for C-C bond coupling.

Conclusions:

• The Zn40Zr60O/CsX tandem catalyst efficiently utilizes CO2 for MEPY alkylation.
• Dual functions of the catalyst (CO2 hydrogenation and C-C coupling) are crucial for performance.
• The CHxO* intermediate, not methanol, drives the C-C bond coupling reaction.