(397i) Understanding the Performance of Slipped Covalent Organic Frameworks for CH4 Storage and CO2:CH4 Separation Using Fixed Bed Adsorption Column

Methane (CH₄) is a major component of natural gas and used as a replacement of petroleum in automobile applications, due to economic and environmental concerns. For the on-board storage of methane, adsorption in nanoporous materials offers energy efficient solution compared to compression and liquefication. Therefore, various nanoporous materials like zeolites, metal organic frameworks (MOFs) and covalent organic frameworks (COFs) are being synthesized. Among these materials, COFs have the advantage of light weight and low density, which make them a suitable candidate for light weight gas separation and high gravimetric adsorption applications. To improve the CH₄ storage and separation applications of COFs we explored the effect of slipping between COF layers. We first obtained the CH₄ adsorption isotherms in recently synthesized TpPa1, TpBD and polyimide COFs (PI-COFs) using grand canonical Monte Carlo simulations and assessed their CH₄ storage performance. Further, we obtained the CO₂ adsorption isotherms followed by CO₂/CH₄ adsorption selectivity calculations using ideal adsorbed solution theory (IAST). We also modelled the transient breakthrough characteristics for CO₂:CH₄ separation using fixed bed adsorption column. Our results show huge variation in the CH₄ adsorption and separation performance of COFs with slipping. These results are explained using energy landscape, density distribution and pore characteristics. Our study suggests the potential use of slipped COFs for CH₄ storage and separation via fixed bed adsorption column.