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.