A molecular dynamics study of enhanced CO ₂ separation <i>via</i> boron nitride nanotubes embedded in a silicon nitride membrane

In this work, we performed molecular dynamics (MD) simulations to investigate CO₂ capture from flue gases with boron nitride nanotubes (BNNTs) and BNNTs embedded inside a silicon nitride (Si₃N₄) membrane. The CO₂ molecules preferentially fill and occupy the BNNTs over N₂ molecules. The high selectivity of BNNTs to capture CO₂ rather than N₂ results in a large separation effect. It was found that the CO₂ molecules within the BNNTs form an ordered solid structure. Further to this, we investigated how the separation performance may be enhanced by placing BNNTs inside a silicon nitride (Si₃N₄) membrane. The presence of the Si₃N₄ membrane was found to alter the solid CO₂ structures. This change is attributed to the resulting non-uniform electric field inside the BNNTs. The altered electrostatic and van der Waals interaction experienced by CO₂ due to the presence of the Si₃N₄ membrane leads to an enhancement of the previously mentioned separation effect. This work demonstrates the great potential for BNNTs, in particular those embedded in Si₃N₄ membranes, for use in carbon capture applications.