The authors developed a novel method to synthesize nanosized chabazite (CHA) zeolite crystals without organic templates, achieving high CO₂ capture efficiency and selectivity. Using a colloidal suspension containing only inorganic cations (Na⁺, K⁺, Cs⁺), they produced CHA nanocrystals (~100 nm in size) with a plate-like morphology. This approach eliminates the need for energy-intensive steps like organic template removal, reducing production costs.
The CHA nanocrystals demonstrated exceptional CO₂ adsorption capacity (3.8 mmol·g⁻¹ at 121 kPa) and perfect selectivity over CH₄, attributed to a molecular "trapdoor" mechanism. In this process, CO₂ interacts with Cs⁺/K⁺ cations at the center of the 8-membered ring (8MR) pore openings, temporarily displacing them to allow CO₂ entry while excluding CH₄.
The contribution of our team consisted of analysing the material by electron diffraction, providing crucial quantitative evidence of the amount of absorbed CO2 and its incorporation in the CHA structure. Structure analysis via 3D electron diffraction revealed that there are on average eight CO₂ molecules per unit cell, with extra-framework cations located at key sites (SII and SIII’) governing adsorption.
The material maintained 100% adsorption capacity over 10 cycles, showcasing stability and regenerability. Its performance rivals CHA zeolites synthesized with organic templates, offering a sustainable alternative for industrial CO₂ capture.
Fig.: Identification of nanosized CHA