Evaluating the potential of NUIG2 metal-organic framework for adsorption of short linear alkanes at low pressure

For the first time, metal-organic framework NUIG2 has been investigated for the adsorption and separation of methane (C1), ethane (C2), propane (C3) and butane (C4) at low pressure. To calculate the loading and mobility of the gas molecules inside NUIG2, grand canonical Monte Carlo and molecular dynamics simulations were performed. C2 and C3 had the maximum loading on the framework because of their appropriate molecular size and tightly fitting into the pores. On the other hand, C1 molecules were able to be freely situated in all pores, but C4 molecules were accommodated only into the largest channels. Radial distribution function analysis revealed that methyl and phenyl groups of the framework were the most favorable interaction sites for the gas molecules. The Henry coefficient indicated that the adsorption affinity of the gas molecules into the NUIG2's pores was in the order of C1 < C2 < C3 < C4 following molecular size. The diffusion of C1 molecules were significantly fast, while its loading was high in the framework. However, C3 and C4 molecules demonstrated the least diffusion at different loading. Overall, NUIG2 showed good ability to adsorb short linear alkanes at low pressure. This study also determined that NUIG2 has a high potential for the separation of C1 molecules. Larger channels in NUIG2 are expected to be a very promising site for further study into the selective adsorption of longer chain alkanes.