Direct Air Capture: Recyclability and Exceptional CO₂ Uptake Using a Superbase.

Area of Science:

• Chemical Engineering
• Environmental Science
• Materials Science

Background:

• Direct air capture (DAC) of CO2 faces challenges due to low CO2 concentrations and high humidity in ambient air.
• Conventional methods often struggle with efficiency and stability under real-world conditions.

Purpose of the Study:

• To develop an efficient and reversible CO2 absorbent for DAC from humid air.
• To investigate the performance of a novel deep eutectic solvent (DES) for CO2 capture.

Main Methods:

• A deep eutectic solvent (DES) composed of 1,5,7-triazabicyclo [4.3.0] non-6-ene (TBN) and benzyl alcohol was synthesized.
• The CO2 absorption capacity and desorption kinetics of the DES were evaluated using untreated ambient air with high humidity.
• The stability and recyclability of the DES were tested over 100 absorption-desorption cycles.

Main Results:

• The TBN-containing DES demonstrated a high CO2 absorption capacity of 0.154 gCO2/gDES (3.5 mmol/g) from air with >90% humidity.
• The absorbent retained 74% of its capacity after 50 cycles and 50% after 100 cycles, indicating good recyclability.
• CO2 desorption was achieved at a low temperature of 70°C within 30 minutes.

Conclusions:

• The developed DES exhibits high CO2 capture capacity, excellent stability, recyclability, and moisture insensitivity, making it a promising candidate for DAC.
• This novel liquid absorbent outperforms existing materials in terms of efficiency, recyclability, and practicality for direct air capture applications.