Enhanced Adsorption Efficiency through Materials Design for Direct Air Capture over Supported Polyethylenimine

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Carbon capture and sequestration (CCS) and utilization (CCU) are critical for mitigating rising atmospheric CO2 levels.
• Direct air capture (DAC) offers a solution for sourcing pure CO2 for various applications.
• Existing DAC technologies face challenges in efficiency, particularly with ultradilute CO2 concentrations.

Purpose of the Study:

• To develop innovative materials for highly efficient direct air capture of CO2.
• To investigate the role of material design in enhancing CO2 adsorption efficiency.
• To achieve unprecedented amine efficiency for capturing ultradilute CO2.

Main Methods:

• Synthesized novel adsorbent materials by supporting polyethylenimine (PEI) on pore-expanded MCM-41 (PME).
• PME was functionalized with cetyltrimethylammonium (CTMA+) cations, creating a C16 chain layer.
• Evaluated the CO2 capture efficiency of PEI/PME under dry and humid conditions with ultradilute CO2 (400 ppm).

Main Results:

• The CTMA+ layer on PME significantly enhanced PEI's amine efficiency for CO2 capture.
• PEI/PME demonstrated 2-4 times higher amine efficiency compared to PEI on other silica supports.
• A PEI/PME material with 40 wt% PEI achieved a record 7.31 mmol CO2/g PEI under humid conditions with 400 ppm CO2.

Conclusions:

• Molecular design, specifically amine accessibility influenced by the C16 chain layer, is crucial for adsorbent performance.
• PEI/PME represents a breakthrough in direct air capture technology for ultradilute CO2.
• This advancement offers a promising pathway for efficient CO2 capture and utilization.