Efficient Selective Capture of Carbon Dioxide from Nitrogen and Methane Using a Metal-Organic Framework-Based...

Selective carbon capture from exhaust gas and biogas, which mainly involves the separation of CO₂/N₂ and CO₂/CH₄ mixtures, is of paramount importance for environmental and industrial requirements. Herein, we propose an interesting metal-organic framework-based nanotrap, namely ZnAtzCO₃ (Atz^- = 3-amino-1,2,4-triazolate, CO₃^2- = carbonate), with a favorable ultramicroporous structure and electrostatic interactions that facilitate efficient capture of CO₂. The structural composition and stability were verified by FTIR, TGA, and PXRD techniques. Particularly, ZnAtzCO₃ demonstrated high CO₂ capacity in a wide range of pressures, with values of 44.8 cm³/g at the typical CO₂ fraction of the flue gas (15 kPa) and 56.0 cm³/g at the CO₂ fraction of the biogas (50 kPa). Moreover, ultrahigh selectivities over CO₂/N₂ (15:85, v:v) and CO₂/CH₄ (50:50, v:v) of 3538 and 151 were achieved, respectively. Molecular simulations suggest that the carbon atom of CO₂ can form strong electrostatic C^δ+···^δ-O-C interactions with four oxygen atoms in the carbonate ligands, while the oxygen atom of CO₂ can interact with the hydrogen atoms in the triazolate ligands through O^δ-···^δ+H-C interactions, which makes ZnAtzCO₃ an optimal nanotrap for CO₂ fixation. Furthermore, breakthrough experiments confirmed excellent real-world separation toward CO₂/N₂ and CO₂/CH₄ mixtures on ZnAtzCO₃, demonstrating its great potential for selective CO₂ capture.