Molecular Simulation Evaluation on C₂H₂/CO₂ Selective Adsorption in CoV-tcb Pacs-Type Metal-Organic Frameworks

Separation of acetylene (C₂H₂) from carbon dioxide (CO₂) is a challenging and important problem in industry. Recently, Feng et al. and Bu et al. proposed a strategy that combined the bioisosteric (BIS) strategy with pore space partition (PSP) to prepare the CoV-tcb pacs-type metal-organic frameworks (MOFs) in order to improve the selectivity of C₂H₂/CO₂ in the experiment (Wang et al., J Am Chem Soc, 2023, 145(32): 17551-17556). With the BIS-PSP strategy, CoV-tcb pacs-type MOFs (the same as CPM-110 pacs) show higher selectivity than CoV-bdc pacs-type MOFs (same as CPM-733 pacs), which were designed by the PSP strategy. However, their microscopic mechanism still needs to be further explored. In this context, molecular simulations have been performed to observe and analyze the adsorption process. Here, we calculated the influence of CoV-tcb and CoV-bdc pacs-type MOFs on separation selectivity for C₂H₂/CO₂ through the grand canonical Monte Carlo (GCMC) method. CoV-tcb-tpt shows a C₂H₂/CO₂ (99/1) selectivity of 6.72. The further density distributions revealed by the BIS strategy showed that there was no gas absorption inside the o-cages in CoV-tcb pacs-type MOFs, whereas the CoV-bdc pacs-type MOFs showed an opposite conclusion. The calculation proves that the BIS-PSP strategy increases the C₂H₂/CO₂ selectivity, which can be used to design more MOFs for gas separation.