Enhancing the adsorption and separation performance of covalent organic framework by interlayer slipping

Developing novel materials for gas separation and storage is need of the hour due to the increasing demand of energy and production of greenhouse gases leading to climate change. Nanoporous materials offer a potential route... [ view full abstract ]

Developing novel materials for gas separation and storage is need of the hour due to the increasing demand of energy and production of greenhouse gases leading to climate change. Nanoporous materials offer a potential route for these applications with less energy consumption and low cost, compared to other techniques such as chemisorption in liquid solutions, mineralization, storage in pressurized containers etc. Therefore, various nanoporous materials like zeolites, metal organic frameworks (MOFs) and covalent organic frameworks (COFs) are being synthesized.

In this talk, I would be focusing on layered COF materials. Though current COFs have lower adsorption performance, compared to zeolites and MOFs, however, they are ideal candidates for light weight gas separation columns and high gravimetric adsorption applications due to their lower density. Therefore, with the aim to improve the properties of COFs, we explored the effect of slipping between COF layers on their gas separation and adsorption performance. We have used multiscale simulation technique to study CO2, N2 gas adsorption and separation in recently synthesized TpPa1, TpBD and polyimide (PI) COFs. We obtained the single component adsorption isotherms and analyzed the energetics of individual gases in them. Further, we calculated the mixture CO2/N2 adsorption selectivity using ideal adsorbed solution theory (IAST). We combined the mixture prediction capacity of IAST with the mathematical model of fixed bed adsorption column to obtain the transient break through analysis for CO2/N2 separation. Our results show drastic variation in separation and adsorption performance of COFs with slipping, and the optimized COFs have 3 times higher adsorption and separation capacity compared to non-slipped COFs. The performance of slipped COFs is better than previously reported COFs and is comparable to MOFs and zeolites. The obtained understanding would be useful in the design of new nanoporous materials.