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

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