Versatile CO₂ Hydrogenation-Dehydrogenation Catalysis with a Ru-PNP/Ionic Liquid System.

Area of Science:

• Catalysis
• Green Chemistry
• Materials Science

Background:

• Developing efficient catalytic systems for CO2 utilization and hydrogen storage is crucial for sustainable energy.
• Reversible conversion between CO2 and formic acid offers a promising pathway for chemical energy storage.
• Ionic liquids (ILs) can enhance catalyst stability and activity.

Purpose of the Study:

• To develop a novel catalytic system for the reversible hydrogenation of CO2 and dehydrogenation of formic acid (FA).
• To investigate the synergistic effects of Ru-PNP complexes and ILs on catalytic performance.
• To evaluate the potential of this system for CO2 conversion and hydrogen release applications.

Main Methods:

• Synthesis and characterization of Ru-PNP complexes.
• Immobilization of Ru-PNP complexes in ionic liquids.
• Testing catalytic activity for CO2 hydrogenation and FA dehydrogenation under various conditions (temperature, pressure, flow).
• Assessing catalyst stability and recyclability over multiple cycles.

Main Results:

• High catalytic activity for CO2 hydrogenation at 25 °C and 1 bar CO2/H2, yielding 14 mol % FA.
• Achieved 126 mol % FA/IL at 40 bar CO2/H2 with a STY of 0.15 mol L-1 h-1.
• Successful conversion of CO2 from simulated biogas.
• High turnover frequencies (up to 11,000 h-1) for FA dehydrogenation under heat-integrated conditions (<100 °C).
• Catalyst demonstrated exceptional stability over 13 cycles with a turnover number exceeding 18,000,000.

Conclusions:

• The Ru-PNP/IL system is a highly active and stable catalyst for reversible CO2/FA conversion.
• This system operates under mild conditions, making it suitable for energy-efficient applications.
• The Ru-PNP/IL system shows significant potential as a CO2/FA battery, H2 releaser, and CO2 converter.