Confinement effects facilitate low-concentration carbon dioxide capture with zeolites

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Engineered systems for atmospheric carbon dioxide (CO₂) removal require advanced adsorbent materials.
• Current adsorbents often lack the efficiency and capacity needed for effective CO₂ capture, especially at low concentrations.

Purpose of the Study:

• To investigate synthetic mordenite (MOR)-type zeolites as adsorbents for capturing low-concentration CO₂.
• To understand the structure-performance relationship governing CO₂ adsorption in MOR-type zeolites.

Main Methods:

• Synthesis of MOR-type zeolites with varying properties.
• CO₂ adsorption experiments using volumetric and gravimetric methods at low concentrations (400 ppm).
• Structure-performance analysis to identify key adsorption sites and influencing factors.

Main Results:

• MOR-type zeolites exhibit fast kinetics, low heat of adsorption, and high CO₂ capacity (up to 1.15 mmol/g).
• Sodium cations (Na⁺) in the O33 site of the MOR framework are identified as primary CO₂ adsorption sites.
• CO₂ adsorption capacity increases to ~2.0 mmol/g at subambient temperatures and is influenced by pore space size.

Conclusions:

• MOR-type zeolites demonstrate significant potential as effective adsorbents for atmospheric CO₂ capture.
• The specific cation sites and pore structure of zeolites are critical for efficient low-concentration CO₂ adsorption.
• These findings pave the way for developing improved materials for direct air capture technologies.