(369d) Screening of Copper Open Metal Site MOFs for Olefin/Paraffin Separations Using DFT Derived Force Fields

Industrial production of ethylene and propylene involves a catalytic cracking process that is followed by high-pressure cryogenic distillation of light olefin/ paraffin mixtures. Due to their importance to the chemical and polymer industry, efficient adsorption processes for olefin/paraffin separations are likely to result in significant energy savings. Although a small number of Metal Organic Frameworks (MOFs) have been experimentally evaluated, large-scale computational screening studies are not available due to the difficulty in describing the complex interactions of the olefin with the open metal site (OMS).

In this work, we develop new Density Functional Theory derived force fields (FFs) that accurately reproduce the experimental adsorption isotherms C₂ and C₃ hydrocarbons in CuBTC. Further, by using extensive DFT calculations, we demonstrated that the FF transferable to other MOFs containing open Cu sites. Using these transferrable force fields, we evaluate the performance of 94 distinct Cu-OMS MOFs for the industrially important propylene/propane separation, and identify 20 MOFs that are predicted to have attractive properties as adsorbents. Our approach is easily applicable to related olefin/paraffin separations in Cu OMS MOFs and to MOFs with other under-coordinated metal sites.